To provide a rotation detection system which can improve angle detection accuracy free of influence from an offset signal caused by distortion of a silicon chip.

The rotation detection system comprises a magnetic sensor array and a magnet which rotates facing the magnetic sensor array. Each sensor element of the magnetic sensor array constitutes a sensor element group 16 of four sensor elements arranged in the longitudinal and latitudinal four directions. The sensor element groups 16 are connected in parallel to form a sensor pixel 17.