A sealing plate for a prismatic secondary battery includes a pair of mouths for attaching a negative and positive electrode terminals, one mouth being formed near one end in a longitudinal direction of the sealing plate, and the other mouth being formed near the other end, coining areas used for positioning of an insulating member and formed around the pair of mouths on a front face of the sealing plate, a gas release valve and an electrolyte pour hole formed between the pair of mouths, and grooves formed between the respective coining areas and the long side edge of the sealing plate. The groove has a smaller depth near the gas release valve than the depth near the coining area. Even when the sealing plate is produced through forging, the front face has good flatness and the coining areas are unlikely to have a sink mark or a shear drop.