Event.delta

설명

The relative movement of the mouse compared to last event.

Used in EventType.MouseMove, EventType.MouseDrag, EventType.ScrollWheel events.

See Also: Event.mousePosition.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void OnGUI() {
        Event e = Event.current;
        if (e.isMouse)
            Debug.Log(e.delta);
        
    }
}