A rotation detecting device includes a member to be detected, and a sensor section arranged opposite the member to be detected. The sensor section includes two magnetic sensors, each including a detecting portion to detect a magnetic field produced from the member to be detected, with the detecting portions of the sensors being arranged in such a manner as to overlap each other in an opposite arrangement direction of the sensor section and the member to be detected, and a housing provided to cover the sensors together, and including an opposite surface to the member to be detected. The detecting portion of one of the sensors, which is arranged in a side of the sensor section close to the member to be detected, is arranged in such a manner as to be inclined with respect to the opposite surface of the housing.