A rectangular tube-like connection portion (11) is constituted of a bottom plate (13), a first side plate (14), a top plate (not shown), and a second side plate. A movable contact piece (20) is attached at its base portion (20a) to the rear of the bottom plate (13), an intermediate portion of the movable contact piece is formed in a mountain-like shape, and the top of the mountain-like shape is acontact portion (20d) coming into contact with a mating insertion terminal to be inserted. The movable contact piece (20) is folded over the bottom plate (13) before the connection portion (11) is formed. There is a cutout in the bottom plate (13), a rectangular reinforcement piece (not shown), connected at its rear portion to the bottom plate (13), is lifted upward from the bottom plate (13), and a front-end portion of the reinforcement piece is in contact with a lower face of the contact portion (20d) of the movable contact piece (20). At the entrance of the connection portion (11), a guidepiece (22) provided at the head of the bottom plate (13) is bent inward and covers a free end (20c) of the movable contact piece (20), preventing the free end from moving upward and guiding the insertion terminal.