To provide a grinding device in which high electrode position accuracy is unnecessary when a grinding wheel is mounted on a wheel mount, defective electrode contact is not generated even when a node area is changed during ultrasonic vibration machining, and the grinding wheel can be easily mounted on and dismounted from.

In the grinding device, a fixed electrode (62) having magnetic force is arranged on the wheel mount (31), and a movable electrode part (71) including a movable electrode 713 to be attracted by magnetic force is housed in a housing part (413a) of a wheel base (413) in such a manner as to be moved back and forth. When the wheel mount (31) is mounted on the wheel base (413), due to magnetic force of a magnet (622) formed with south and north poles arranged in parallel with a contact face (621a) of the fixed electrode (62), the movable electrode part (71) is brought into contact with the fixed electrode (62) to energize a circular ultrasonic vibrator (415), whereas the movable electrode part (71) is released from contact with the wheel base (413).