A method of manufacturing a face gear comprising, deriving a path of contact of a face gear including a plurality of gear teeth in meshing with a pinion gear, the face gear teeth including a first tooth flank (lid) and a second tooth flank (lie), processing the tooth flanks (11d, 11e) based on the path of contact, wherein the deriving of a path comprises: positioning the pinion gear for meshing with the face gear at a prescribed reference contact position; shifting the pinion gear from the reference contact position either towards or away from the face gear along a rotational axis of the face gear; deriving a first relationship between a rotational angle of the pinion gear and a fluctuation error of a rotational angle of the face gear; deriving a second relationship between the rotational angle of the pinion gear and the fluctuation error by shifting the first relationship by subtracting from the rotational angle an angle of 360 degree divided by the number of the gear teeth; deriving a third relationship between the rotational angle of the pinion gear and the fluctuation error by shifting the first relationship by adding to the rotational angle the angle of 360 degree divided by the number of the gear teeth; deriving a first point which the first and second relationships share and a second point which the first and third relationships share, the first point having a first fluctuation error, the second point having the first fluctuation error; deriving a third point, which has the first fluctuation error, between the first and second points as the intersection between a first straight line connecting the first point and the second point and a second straight line perpendicularly extended to the first straight line from an error position of the first relationship arranged between the first point and the second point; calculating a transmission error by subtracting the first fluctuation error from a fluctuation error at said error position; and determining a curve line connecting a first contact position, a second contact position, and a third contact position as the path of contact on the tooth flanks (11d, 11e) of the gear teeth of the face gear, the first contact position being set as a contact position of the pinion gear and corresponding to the first point, the second contact position being set as a contact position of the pinion gear and corresponding to the second point, the third contact position being set as a contact position of the pinion gear and corresponding to the third point when the face gear is rotated by the amount of the transmission error. positioning the pinion gear for meshing with the face gear at a prescribed reference contact position; shifting the pinion gear from the reference contact position either towards or away from the face gear along a rotational axis of the face gear; deriving a first relationship between a rotational angle of the pinion gear and a fluctuation error of a rotational angle of the face gear; deriving a second relationship between the rotational angle of the pinion gear and the fluctuation error by shifting the first relationship by subtracting from the rotational angle an angle of 360 degree divided by the number of the gear teeth; deriving a third relationship between the rotational angle of the pinion gear and the fluctuation error by shifting the first relationship by adding to the rotational angle the angle of 360 degree divided by the number of the gear teeth; deriving a first point which the first and second relationships share and a second point which the first and third relationships share, the first point having a first fluctuation error, the second point having the first fluctuation error; deriving a third point, which has the first fluctuation error, between the first and second points as the intersection between a first straight line connecting the first point and the second point and a second straight line perpendicularly extended to the first straight line from an error position of the first relationship arranged between the first point and the second point; calculating a transmission error by subtracting the first fluctuation error from a fluctuation error at said error position; and determining a curve line connecting a first contact position, a second contact position, and a third contact position as the path of contact on the tooth flanks (11d, 11e) of the gear teeth of the face gear, the first contact position being set as a contact position of the pinion gear and corresponding to the first point, the second contact position being set as a contact position of the pinion gear and corresponding to the second point, the third contact position being set as a contact position of the pinion gear and corresponding to the third point when the face gear is rotated by the amount of the transmission error.