Make object follow mouse cursor in 2D

I’m makin a game in Unity 2D, and need an object to follow the mouse movement in order to make a custom and changeable cursor. This is the code I have currently. At the moment, it follows the mouse, but is displaced from the mouse about of of the screen to the top left, i.e. if the mouse is at the bottom left of the screen, the cursor is in the middle.

Current Code:

using UnityEngine;
using System.Collections;

public class Cursor : MonoBehaviour {

	

	// Use this for initialization
	void Start () {
		Screen.showCursor = false;
	}
	
	// Update is called once per frame
	void Update () {
		Vector3 mouse = Input.mousePosition;
		mouse = mouse * 10F;
		transform.position = Camera.main.ScreenToViewportPoint(mouse);

	}
}

mouse = mouse * 10F;

why is that for? If your mouse is at (10,10) then you get at (100,100) then the conversion goes also wrong.