A lead pin includes a shaft portion, a connection head portion provided to a top end side of the shaft portion, and having a diameter which is larger than a diameter of the shaft portion, wherein the connection head portion includes a bonding surface on an opposite side to the shaft portion side, and the bonding surface includes a flat surface provided in a center part, a convex surface which is provided like a ring shape to an outside of the flat surface and rounded by a radius R like a convex shape, and a concave surface which is provided like a ring shape to an outside of the convex surface and rounded by a radius R like a concave shape.