A rotation angle sensor includes a sensor integrated circuit attached to an attachment member. The attachment member includes a connecting terminal protruding upward from an attachment surface and a guide protruding upward from the attachment surface and positions, together with the connecting terminal, the sensor integrated circuit at an attachment position. The sensor integrated circuit includes a lead frame on which an electronic circuit is mounted and an exterior covering the electronic circuit. The lead frame includes a lead and an extending portion located in an outer periphery of the exterior. At least one of the lead and the extending portion has an elastic structure. The sensor integrated circuit is attached to the attachment member by an elastic force of the elastic structure that biases the extending portion against the guide and that joins the lead to the connecting terminal.