The present invention achieves a machining apparatus which can easily be composed and a machining method which can perform gear machining or splined shaft machining easily by using an existing lathe. More specifically, the invention achieves a machining apparatus 1 comprising: a cutter 11 which includes a blade part 20 formed in the shape of a ring around a peripheral surface thereof and which is driven to rotate about an axis thereof; a workpiece holder 13 which holds a workpiece W rotatably; and a cutter driver 12 which moves the cutter 11 and the workpiece W relative to each other along an axial direction, wherein a gear or a splined shaft is formed on the peripheral surface of the workpiece W by synchronizing the rotation of the workpiece W with the relative movement of the cutter 11 and the workpiece W and by rotating the cutter 11, and wherein a plurality of the blade parts 20 are disposed side by side along the axis, the cutter driver 12 drives the cutter 11 to rotate in one direction around the axis and to reciprocate relative to the workpiece W along the axis, the workpiece holder 13 rotates the workpiece W in a forward/reverse direction in accordance with reciprocation of the cutter 11, and cutting is performed on the workpiece W so as to form thereon an external shape of a gear or a splined shaft by placing each of the blade parts 20 of the cutter 11 in contact with the peripheral surface of the workpiece W.

A gear machining apparatus includes a machining tool having a plurality of protruding tool edges on an outer periphery of the machining tool, and driving apparatuses that form a tooth on a work piece by rotating the machining tool around a central axis thereof, rotating the work piece W around a central axis thereof, and moving the machining tool relative to the work piece. Radial outer faces of the protruding tool edges form multiple steps that are parallel to the central axis of the machining tool such that the diameter of the machining tool increases in a stepwise manner from a tool leading end toward a tool base end of the machining tool.