A rotation detector includes a rotary member, a magnet rotating as the rotary member rotates, and a first magnetic sensor detecting a direction of magnetic flux that changes as the magnet rotates. And the rotation detector includes a first soft magnetic member and a second soft magnetic member for the first magnetic sensor that are arranged on one side and the other side, respectively, of a detection direction of the first magnetic sensor. The magnet has a rotation axis that passes through the magnet.