Insulators each include a plurality of board holding claws projecting from an outer peripheral edge of the circuit board for engaging a plurality of board recesses, the plurality of board holding claws are arranged on the outer peripheral edge of the circuit board such that an interval of board holding claws on a connector-mounted side is smaller than an interval between board holding claws on a counter-connector-mounted side, and a load receiving pin, which receives a radial load, projects at a counter-connector-mounted position, which is opposite to a mounted position of a connector.