A seat switch assembly can maintain a reliable switching operation due to enhanced durability. A pressing plate has guides which are fastened to guide holes of a base. A seat switch housing is fastened to an assembly hole of the base. An actuation rod is received inside a through-hole of the seat switch housing, and moves in the top-bottom direction in response to a pressure from the pressing plate. A V-shaped contact pin is fixed to a fixing guide of the actuation rod. One portion of a terminal pin is buried inside the seat switch housing, and the other portion of the terminal pin is exposed to the outside. A return spring is received in the lower portion of the actuation rod. A cover closes the lower portion of the through-hole. The inner surfaces of the through-hole and the terminal pin are coplanar without a stepped portion.