To provide a grid type polarizing optical element usable from a visible light area to an infrared light area, and to provide a method for continuously manufacturing the polarizing optical element.

A PET film 12 is supplied through a roll 13, and mixed liquid constituted of polyvinyl alcohol, formaldehyde, metal-processed ZnO whisker and water of prescribed thickness is applied on the surface of the PET film by using a T-die 14, next, the film is coated while adding shearing stress by making the circumferential velocity of the upper part 16 of a two-axle roll differ from that of the lower part 16'. In this case, the ZnO whisker is oriented in a film length direction. Next, the film is dried/hardened through an air-conditioned tank 17 which is maintained at a prescribed temperature and a roll 18, thereafter, the film is taken up by a take-up roll 19. The obtained film-like polarizing optical element has an extremely high polarizing reflecting performance in a wavelength band of 1μm to 10μm of the infrared ray, and the infrared ray reflectance of the element is 99% in a state where the optical element is made orthogonal to the infrared ray.