An encoder 12 a characteristic of which is changed alternately at an equal interval in a circumferential direction is supported/fixed onto a hub 4 concentrically with the hub4. A sensing portion of a sensor 13 supported on the outer ring 3 is positioned in close vicinity to a sensed surface of the encoder 12 to face thereto. Width dimensions of first and second sensed portions provided onto the sensed surface are changed continuously in a direction along which a to-be-sensed load is applied. Since a pattern according to which an output signal of the sensor 13 is changed is changed pursuant to a change of the load, the load is derived by observing this pattern. The output signal is also utilized to sense a rotation speed of the hub 4 in ABS or TCS control.