A projection display system includes a projection display unit and a member in a form of one of a windable screen, a white board and a notice board. The projection display unit projects an image light onto a projection plane of the member to display an image thereon. The projection display unit includes a light source, an image display element, a lighting optical system irradiating a beam of light from the light source on the image display element, and a projection optical system projecting the image light from the image display element toward the member. The projection optical system includes, in order toward the member from the image display element, a front lens group, and a reflecting mirror shaped to be axial-asymmetrical with respect to the optical axis.