A rolling bearing unit having a sensor comprising: a first raceway member, on the outer circumferential surface of which a raceway surface is provided; a second raceway member, on the inner circumferential surface of which a raceway surface is provided; a plurality of rolling elements arranged between the raceway surface of the first raceway member and the raceway surface of the second raceway member; a base plate, the shape of which is formed into an annular and flat shape, having a through-hole that the first raceway member penetrates; a first coil, the shape of which is formed into a plane shape, arranged so that the first coil surrounds an overall circumference of the first raceway member; and a plurality of second coils, the shape of which is formed into a plane shape, arranged around the first coil.