A surface-treated metal plate including: a metal plate; and a nickel-cobalt binary alloy layer formed on the metal plate. When a part having a content ratio of oxygen atoms of 5 atomic % or more as measured by X-ray photoelectron spectroscopic analysis is an oxide coating film, the nickel-cobalt binary alloy layer contains the oxide coating film with a thickness of 0.5 to 30 nm on a surface thereof, and when a pressure cooker test including temperature increasing, retention for 72 hours under a water-vapor atmosphere at a temperature of 105° C. and a relative humidity of 100% RH, and temperature decreasing is performed, the amount of increase in the thickness of the oxide coating film is 28 nm or less.