Gear processing device

The present invention provides a gear processing device, which comprises: an annular housing; a ring-shaped tool support body rotatably disposed on the inner peripheral side of the housing; an internal gear-shaped tool attached to the inner peripheral side of the tool support body and meshing with the gear to be machined; and a fixing mechanism for fixing the tool to the tool support body. The fixing mechanism includes at least one port portion provided in the tool support body for allowing oil to flow in from the outside and discharging the oil to the outside; an annular flow path formed in the circumferential direction on the inner peripheral surface of the tool support body and communicating with the port portion; and a deformable member that is configured to be deformable so as to be in close contact with an inner peripheral surface of the tool support body and to press the outer peripheral surface of the tool by an inflow of oil into the annular flow path. This enables efficient attachment and detachment