Shadowless Projector is projection mapping system in which a shadow (more specifically, umbra) does not suffer the projected result. A typical shadow removal technique used a multiple overlapping projection system. In this paper, we propose a shadow-less projection method with single projector. Inspired by a surgical light system that does not cast shadows on patients' bodies in clinical practice, we apply a special optical system that consists of methodically positioned vertical mirrors. This optical system works as a large aperture lens, it is impossible to block all projected ray by a small object such as a hand. Consequently, only penumbra is caused, which leads to a shadow-less projection.