Provided is a polarizing plate having a wire grid structure, including: a transparent substrate; grid-shaped protrusions that are arranged in a one-dimensional grid shape on the transparent substrate at a pitch shorter than a wavelength of light in a use band and extend in a predetermined direction, in which the grid-shaped protrusions include a first grid-shaped protrusion group arranged, at a first pitch P1 and a second grid-shaped protrusion group arranged at a second pitch P2 between the adjacent grid-shaped protrusions of the first grid-shaped protrusion group, and in which a width W1 of the grid-shaped protrusion in the first grid-shaped protrusion group is larger than a width W2 of the grid-shaped protrusion in the second grid-shaped protrusion group. In addition, provided is an optical device including the polarizing plate.