Provided is a gear device capable of resolving inconveniences such as abnormal wear that arises due to the relative misalignment between the internal gear pins and the external gear, and inhibiting an increase in the number of components. This gear device has an outer cylinder, internal gear pins, and a carrier. A plurality of pin grooves extending in the axial direction of the outer cylinder are formed on the inner peripheral face of the outer cylinder, and the internal gear pins are fitted in the pin grooves. The pin grooves are formed so that the length of the pin grooves becomes longer than the length of the internal gear pins. The carrier has a pair of pressing members which includes a pressing surface. The pressing surface is configured to regulate movement of the internal gear pins and an oscillating gear which includes external teeth in the axial direction.