A polarization splitting device includes a polarization beam splitter having a polarization splitting surface and allows P-polarized light to transmit therethrough and reflects S-polarized light. A subwavelength structure grating is formed on the polarization splitting surface with a grating pitch smaller than wavelength of incident light. The polarization splitting device also includes a polarizer that is arranged on an optical path of light reflected from the polarization beam splitter and has a transmission axis that is parallel to a polarization direction of the S-polarized light.