A bearing unit with a rotational speed detection unit has a tone wheel which has recesses on its outer peripheral surface and rotates with the magnetic hub and the inner ring, a sensor which has a first stator with notches and a second stator, and a permanent magnet, so that due to the changes in phase of the notches and recesses, the density of the magnetic flux from the permanent magnet is changed, with the magnetic flux led to the second stator and to the hub and inner ring, whereby the number of winding in the coil is increased.