We propose an optical feedback to visualize the virtual touch panel used in the prototype dialysis patient bed. Projection mapping is optical feedback on the position of the virtual touch panel. The virtual touch panel is visualized when the fingertip touches it. Firstly, we experimented the shape and color of the optical feedback. The most selected optical feedback was White Line of Back Side and Blue Space. Secondly, We evaluated operability of the optical feedback. As an analysis result, average of the tap depth was shallow.