To provide a technology capable of reducing the volume of a cabinet for a projection unit when there is no need to project an image.

A cabinet 10 for a projection unit comprises a frame body 20, an upper panel 30, a lower panel 40, a left side 50 and a right side panel 60. The upper panel 30 is turned so as to include the built-up position at which a reflection mirror 11 reflects light from an optical unit 1 toward a screen unit 2, and the folding position. The lower panel 40 is turned so as to include the built-up position at which the optical unit 1 can be arranged, and the folding position. The left side panel 50 and the right side panel 60 are turned so as to include the built-up position at which the left side panel 50 and the right side panel 60 are in line contact with the upper panel 30 and the lower panel 40, and the folding position.