In a pair of mutually connectable terminals, one terminal is provided with a joint having a spherical surface formed on the outer circumferential surface, and the other terminal is provided with a hole into which the joint can be fitted. At least one of the joint and the hole is formed in a plate member which can be displaced elastically in the fitting direction of the joint and the hole. When the pair of terminals are connected, the joint touches the circumferential edge of the hole to displace the plate member elastically. When the joint is fitted in the hole, the plate member is reset elastically and holds the spherical surface of the joint under such a state as the spherical surface is pressed against the edge of the hole.