To increase the usage efficiency of the light of optical elements used in a projection display device, a polarizing conversion unit is provided. This polarizing conversion unit consists of a unit frame, two polarizing conversion element arrays, a light-shielding plate, a lens array, and clips. From the side of one open surface of the unit frame, the two polarizing conversion element arrays are inserted, and the light-shielding plate and the lens array are inserted from the side of the other open surface in this order. These optical elements are clamped by four clips from the two directions of up and down in a state of being stored in the unit frame. Since the clips are formed of an elastic body, the clips can be easily attached and detached, and the respective parts of the polarizing conversion unit can also be easily attached and detached to and from the unit frame. In addition, these optical elements may be sequentially inserted from the side of one open surface.