A prism optical system including an optical low-pass filter disposed on an incident side of a luminous flux, and a prism arranged to perform a color separation to a plurality of color bands by an optical thin film, the prism optical system includes the optical low-pass filter disposed on an incident side of the prism, and at least two quarter-wave plates having a phase elimination function, and each disposed on one of an incident surface and an outgoing surface of the luminous flux of the optical low-pass filter. The prism optical system is configured to satisfy the following equation, |X1/X2|>0.7 where X1 is a phase elimination efficiency at 550 nm wavelength when the incident side quarter-wave plate is inserted between crossed nicols, and X2 is a phase elimination efficiency at 550 nm wavelength when the outgoing side quarter-wave plate is inserted between the crossed nicols.