A gear device is provided with inner-tooth pins fitted into pin grooves of an outer cylinder, a carrier housed inside the outer cylinder, a crankshaft rotatably supported on the carrier, an oscillating gear having outer teeth meshable with the inner-tooth pins and configured to oscillate in conjunction with rotation of the crankshaft, while the outer teeth are meshed with the inner-tooth pins, and a restriction member configured to restrict movement of the inner-tooth pins in an axial direction. The restriction member is mounted to the outer cylinder on an outer side of the outer cylinder.