To provide a polarizing plate and an optical apparatus capable of improving durability while maintaining excellent optical characteristics. Provided is a polarizing plate 1 with a wire grid structure, including: a transparent substrate 10; and a grid-shaped convex portion 11 which is arranged on the transparent substrate 10 at a pitch P shorter than a wavelength of light of a use band, extends in a predetermined direction, and includes a reflection layer 12 formed of a light reflective material, wherein a surface of the grid-shaped convex portion 11 and a surface of a bottom surface portion of a groove formed between the grid-shaped convex portions 11 are provided with a protection film 20 which covers the surfaces thereof and the protection film 20 is formed by two kinds or more of protection films including an organic film formed of an organic material.