To provide a pre-polarizer of low manufacturing cost.

This pre-polarizer 5 is a prism array in which a plurality of compound prisms are linked together comprising a first glass parallelogram prism 7, a 1/2 wavelength plate 8 and a second glass parallelogram prism 9, both ends of the array are held between glass triangular poles 6, 6. The first glass parallelogram prism 7 is formed with a mirror film 10 on the face coming into contact with the second glass parallelogram prism 9, and is formed with a polarizing film 11 on the face coming into contact with the 1/2 wavelength plate 8. The second glass parallelogram prism 9 is formed with a mirror film 12 on the face that comes into contact with the first glass parallelogram prism 7.