The inventive device includes a work supporting portion for supporting a work rotatably about a first axis, a cutter supporting portion for supporting a cutter rotatably about a second axis different from the first axis and a moving portion for moving the cutter along a reference line extending through the first axis. The second axis is slanted relative to a reference plane oriented perpendicular to the first axis and a blade edge of the cutter is caused to come into contact with the work at an offset position offset from the reference line. The work and the cutter are driven in synchronism and the cutter is moved along the reference line.

There is provided a tool for efficiently cutting a face gear to be meshed with a helical gear. When a circular tooth thickness of a tooth tip of a cutting edge portion is represented as S.sub.atSC, a circular tooth thickness on a virtual outside diameter of a tooth profile of the helical gear in a cross-sectional view perpendicular to an axis is represented as S.sub.at, a helix angle on the virtual outside diameter of the tooth profile of the helical gear in a cross-sectional view by a plane perpendicular to the axis is represented as .sub.a, and a face width of the cutting edge portion is represented as b.sub.sc, $b_{\mathrm{SC}}\frac{s_{\mathrm{at}}-s_{\mathrm{atSC}}}{\tan {}_a}$
is satisfied.