To provide a polarizing plate that maintains high durability under high temperature and high humidity conditions, particularly a wire grid polarizing plate.

A wire grid polarizing plate has plural linear and substantially parallel grooves on the surface of a transparent substrate, and has a metal thin film formed on the inner surface of the groove, the wire grid polarizing plate having the following characteristics: (1) the groove has a groove width of 30-300 nm, a groove depth of 100-300 nm and a groove interval of 50-200 nm, and (2) the metal thin film contains at least one selected from the group consisting of nickel, zinc, aluminium, tin, tantalum and chromium and has a thickness of 10 nm or less.