To reduce a gear noise by shock eliminating tooth-to-tooth colliding force by a simple structure, relating to noise reduction when a gear device is in no-load operation.

A driven gear 2 is connected to a driven shaft 4 by providing a space 8 in a diametric direction, and also the driven gear 2 and shaft 4 are connected in the direction of rotation with a key 5 by providing a space 12 in a circumferential direction. An elastic member 6 is compressed in an axial direction to be set up between a lock washer 7 connected to the driven shaft 4 and the driven gear 2.