To provide a device for mounting a disc-shaped rotary tool in which the construction is simple and vibration thereof can be suppressed during use.

The disc-shaped rotary tool (15) having a grinding surface (17) on an outer circumferential part thereof is provided with annular holding grooves (18) on an inner circumferential part thereof. The annular holding grooves (18) are fitted with exposed ring-shaped shock-absorbing bodies (30). A pair of holding bodies (20) are provided so as to face the both sides of the inner circumferential part of the disc-shaped rotary tool (15). The holding bodies (20) hold the both sides of the inner circumferential part of the disc-shaped rotary tool (15) through the shock-absorbing bodies (30) and the axial center part of the holding bodies (20) is fitted to an output shaft (11) of an electric motor (10) to fix integrally.