Conventionally, there are rolling bearing apparatuses to which a rotation detector is installed. There are a passive type and an active type in such rotation detector. The active type can detect a non-rolling state, thereby achieving rotation detection with high precision. The active-type rotation detector includes a pulser ring and a magnetic sensor. The pulser ring is made of a multipolar magnet in which the north pole and the south pole are alternately disposed in a circumferential direction and mounted on the rolling element side out of the inner ring and the outer ring of the rolling bearing. The magnetic sensor is mounted on the non-rolling element side of the rolling bearing opposing the pulser ring. As for the operation, pulse signals are to be outputted from the magnetic sensor according to the rotation of the pulser ring which synchronously rotates with the rolling element and the rotation state of the rolling element is detected by processing the pulse signals. In order to further improve the accuracy of the rotation detection in such active-type rotation detector, it is proposed to reduce each pitch of the magnetic poles of the pulser ring. However, there is a limit in reducing the pitch, which results in limiting the improvement in the accuracy of the rotation detection.