Abstract: An apparatus and a method for machining a gear shape whereby when a gear is machined with a form tool, sludge is easily excluded and an accurate gear shape is provided. A method for machining an accurate gear shape whereby with a workpiece chucked, postprocess steps such as grinding and lapping are performed for consistent machining from material to completion of the gear shape, thereby removing a handling error caused by re-chucking the workpiece. A form tool supplied to a holder that can be rotated and slid in the Z direction by an automatic tool changer and a workpiece held by a chuck mounted on a side table that can be driven in the X and Y directions are synchronously rotated at a mesh assumed position under the control of a control section. Cut amount control is applied between both axes of the workpiece and the form tool and the workpiece is machined with the form tool. Form tools are supplied one after another by the automatic tool changer.