diff --git a/src/pages/Simulation/components/PlanetMesh.tsx b/src/pages/Simulation/components/PlanetMesh.tsx
index c4b7250..059cafc 100644
--- a/src/pages/Simulation/components/PlanetMesh.tsx
+++ b/src/pages/Simulation/components/PlanetMesh.tsx
@@ -5,7 +5,7 @@ import type React from "react";
 import { useEffect, useMemo, useRef } from "react";
 import * as THREE from "three";
 import type { Planet } from "@/types/planet";
-import { calc_gravity_force } from "../utils/gravityUtils";
+import { calcGravityForce } from "../utils/gravityUtils";
 
 type PlanetMeshProps = {
 	planet: Planet;
@@ -89,6 +89,7 @@ export function PlanetMesh({
 	}, [planet.id, planetRegistry, planet.mass, planet.radius, ref]);
 
 	// 計算用ベクトルをメモリに保持しておく（毎フレームnewしないため）
+	const force = useMemo(() => new THREE.Vector3(), []);
 	const forceAccumulator = useMemo(() => new THREE.Vector3(), []);
 	const myPosVec = useMemo(() => new THREE.Vector3(), []);
 	const otherPosVec = useMemo(() => new THREE.Vector3(), []);
@@ -113,13 +114,14 @@ export function PlanetMesh({
 			const otherMass = otherMesh.userData.mass || 1;
 			const otherRadius = otherMesh.userData.radius || 0.1;
 
-			const force = calc_gravity_force(
+			calcGravityForce(
 				myPosVec,
 				planet.mass,
 				planet.radius,
 				otherPosVec,
 				otherMass,
 				otherRadius,
+				force,
 			);
 			forceAccumulator.add(force);
 		}
diff --git a/src/pages/Simulation/utils/gravityUtils.ts b/src/pages/Simulation/utils/gravityUtils.ts
index daf80e6..75d558b 100644
--- a/src/pages/Simulation/utils/gravityUtils.ts
+++ b/src/pages/Simulation/utils/gravityUtils.ts
@@ -1,25 +1,29 @@
-import * as THREE from "three";
+import type * as THREE from "three";
 
 const G = 1;
+const softeningFactor = 0.01;
 
-export function calc_gravity_force(
+export function calcGravityForce(
 	targetPos: THREE.Vector3,
 	targetMass: number,
 	targetRadius: number,
 	sourcePos: THREE.Vector3,
 	sourceMass: number,
 	sourceRadius: number,
-): THREE.Vector3 {
-	const direction = new THREE.Vector3().subVectors(sourcePos, targetPos);
-	const distanceSq = direction.lengthSq();
+	resultVec: THREE.Vector3,
+): void {
+	const EPS = ((targetRadius + sourceRadius) / 2) * softeningFactor;
+
+	resultVec.subVectors(sourcePos, targetPos);
+	const distanceSq = resultVec.lengthSq() + EPS ** 2;
 	const distance = Math.sqrt(distanceSq);
 
-	// 2つの惑星が接触または重なっている場合は、引力を0にする
-	const minDistance = targetRadius + sourceRadius;
-	if (distance < minDistance) {
-		return new THREE.Vector3(0, 0, 0);
+	// 距離が0の場合、力は0として扱う（ゼロ除算を避ける）
+	if (distance === 0) {
+		resultVec.set(0, 0, 0);
+		return;
 	}
 
 	const forceScalar = (G * targetMass * sourceMass) / (distanceSq * distance);
-	return direction.multiplyScalar(forceScalar);
+	resultVec.multiplyScalar(forceScalar);
 }