diff --git a/src/simulations/drawer/random_rule_constructor.ts b/src/simulations/drawer/random_rule_constructor.ts
new file mode 100644
index 00000000..8b4c41cf
--- /dev/null
+++ b/src/simulations/drawer/random_rule_constructor.ts
@@ -0,0 +1,37 @@
+import { random } from "../../classes/utilities"
+import { LSystemCondition } from "./lsystem_rule"
+import { VanillaLSystemRule } from "./vanilla_lsystem_rule"
+
+export const RandomRuleConstructor = {
+  random(): VanillaLSystemRule {
+    const alphabets = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("")
+    const conditions = alphabets.slice(0, random(alphabets.length, 1))
+    const map = new Map<string, LSystemCondition[]>()
+    const maxConditions = 10
+
+    const randomCondition = (): string => {
+      const index = Math.floor(random(conditions.length))
+
+      return conditions[index]
+    }
+
+    conditions.forEach(condition => {
+      const nextConditions: LSystemCondition[] = []
+      for (let i = 0; i < maxConditions; i += 1) {
+        if (random(1) > 0.5) {
+          break
+        }
+        const angle = Math.floor(random(360, 0)) - 180
+        nextConditions.push(angle)
+        nextConditions.push(randomCondition())
+      }
+      if (nextConditions.length === 0) {
+        nextConditions.push(VanillaLSystemRule.endOfBranch)
+      }
+
+      map.set(condition, nextConditions)
+    })
+
+    return new VanillaLSystemRule(map)
+  } 
+}
\ No newline at end of file
diff --git a/src/simulations/drawer/source.ts b/src/simulations/drawer/source.ts
index 6f524bc5..5777b840 100644
--- a/src/simulations/drawer/source.ts
+++ b/src/simulations/drawer/source.ts
@@ -8,6 +8,7 @@ import { VanillaLSystemRule } from "./vanilla_lsystem_rule"
 import { exampleRules } from "./rule_examples"
 import { Downloader } from "./downloader"
 import { TransitionColoredModel } from "./transition_colored_model"
+import { RandomRuleConstructor } from "./random_rule_constructor"
 
 let t = 0
 const canvasId = "canvas"
@@ -99,7 +100,7 @@ function createModel(ruleString?: string): Model {
     for (let i = 0; i < constants.simulation.numberOfSeeds; i += 1) {
       const tries = 20
       for (let j = 0; j < tries; j += 1) {
-        const rule = VanillaLSystemRule.trimUnreachableConditions(VanillaLSystemRule.random(), initialCondition)
+        const rule = VanillaLSystemRule.trimUnreachableConditions(RandomRuleConstructor.random(), initialCondition)
         if (rule.isCirculated(initialCondition)) {
           rules.push(rule)
           break
diff --git a/src/simulations/drawer/vanilla_lsystem_rule.ts b/src/simulations/drawer/vanilla_lsystem_rule.ts
index 96ea7636..2ed96ef0 100644
--- a/src/simulations/drawer/vanilla_lsystem_rule.ts
+++ b/src/simulations/drawer/vanilla_lsystem_rule.ts
@@ -1,4 +1,3 @@
-import { random } from "../../classes/utilities"
 import { Color } from "../../classes/color"
 import { LSystemRule, LSystemCondition, LSystemCoordinate } from "./lsystem_rule"
 
@@ -50,7 +49,8 @@ export class VanillaLSystemRule implements LSystemRule {
     return this._encoded
   }
 
-  private static endOfBranch = "."
+  public static endOfBranch = "."
+  
   private _encoded: string
   private _map: Map<string, LSystemCondition[]>
 
@@ -76,38 +76,6 @@ export class VanillaLSystemRule implements LSystemRule {
     this.transition = this.calculateTransition()
   }
 
-  public static random(): VanillaLSystemRule { // FixMe: 適当に書いたので探索範囲が偏っているはず
-    const alphabets = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("")
-    const conditions = alphabets.slice(0, random(alphabets.length, 1))
-    const map = new Map<string, LSystemCondition[]>()
-    const maxConditions = 10
-
-    const randomCondition = (): string => {
-      const index = Math.floor(random(conditions.length))
-
-      return conditions[index]
-    }
-
-    conditions.forEach(condition => {
-      const nextConditions: LSystemCondition[] = []
-      for (let i = 0; i < maxConditions; i += 1) {
-        if (random(1) > 0.5) {
-          break
-        }
-        const angle = Math.floor(random(360, 0)) - 180
-        nextConditions.push(angle)
-        nextConditions.push(randomCondition())
-      }
-      if (nextConditions.length === 0) {
-        nextConditions.push(VanillaLSystemRule.endOfBranch)
-      }
-
-      map.set(condition, nextConditions)
-    })
-
-    return new VanillaLSystemRule(map)
-  }
-
   public static encode(map: Map<string, LSystemCondition[]>): string {
     const result: string[] = []
     map.forEach((value, key) => {