A combined sensor and bearing assembly including a rolling bearing unit and a rotation sensor unit. The rolling bearing unit is made up of a rotatable raceway member, a stationary raceway member and at least one row of rolling elements. The rotation sensor unit includes a to-be-detected member having a magnet and fitted to one of the raceway members, and a magnetic detecting member fitted to the other raceway member at a location confronting the to-be-detected member. This combined sensor and bearing assembly is used at a location close to an electromagnetic coil emanating a leakage magnetic field, in a condition in which a direction of flow of an electric current through the electromagnetic coil is fixed in one direction so that a direction of a magnetic flux, with which the magnetic detecting member is switched off, may coincide with a direction of the leakage magnetic flux.