Transform.RotateAround

説明

ワールド座標の point を中心とした軸( axis )で angle 度回転させま

これは Transform の位置と回転が同時に変更されます。

using UnityEngine;

//Attach this script to a GameObject to rotate around the target position.
public class Example : MonoBehaviour
{
    //Assign a GameObject in the Inspector to rotate around
    public GameObject target;

    void Update()
    {
        // Spin the object around the target at 20 degrees/second.
        transform.RotateAround(target.transform.position, Vector3.up, 20 * Time.deltaTime);
    }
}