A 3-D mouse system is described that can specify the position and movement of the fingertip in a 3-D space. When mouse-moved event occurs to control the 2-D object on the screen and the 3-D object within the display, a touch panel on the screen can detect the movement of the fingertip. On the other hand, it is necessary to track the fingertip in a space for interaction to the 3-D floating object as the touching image appears out in front of the display, serving as a virtual touch panel in the air. A 3-D position is generally detected and measured using a tereo viewing. A series of two or more stereo images allows us to obtain the 3-D information about the object. However it is possible to estimate the position of fingertip using a single image without stereo images. This paper proposes the measuring method of the position of fingertip using a single camera image. This measuring system can provede 3-D information to control 3-D virtual objects. The system finds out the tip point and width of finger on the image, and approximately calculates the 3-D position of fingertip.