To provide a bearing device with the sensor, in which the sensor can be assuredly fitted and which can be employed in bearing parts of varying sized and be economically manufactured, the bearing device with the sensor including a bearing part having an inner member and an outer member includes an encoder of a revolution sensor unit fitted to the inner member and a sensor fitted to one end of the outer member through a sensor mounting member. The sensor mounting member includes a mounting tube part, mounted on the outer member, and a side plate part axially positioned in contact with the outer member. The side plate includes inner and outer opposite plate portions confronting each other, and sandwiching the sensor therebetween. Alternatively, the side plate part may have a recessed plate section swelling outwardly. The sensor mounting member is of a double structure including inner and outer plates.