Steering-force detection sections, including a pressure-receiving section and a received-pressure detection section, are spaced from one another in the vicinity of a steering shaft. The steering shaft can include a pressing member for applying pressure to the pressure-receiving section when steering handlebars are rotated in either direction to the maximum steering angle. The pressure-receiving section and the received-pressure detection section are coaxially mounted in a pressure-receiving section casing and a detection section casing, respectively, through a guide tube, so that the pressure-receiving directions of both the pressure-receiving sections are parallel to one another and perpendicular to the direction in which the steering-force detection sections are spaced. The detection section casing includes mounting openings for mounting the received-pressure detecting sections and an electric circuit board, which is integrally connected to the received-pressure detecting sections. The mounting openings are formed in the same direction as each other and perpendicularly to the pressure-receiving direction of the pressure-receiving section.