To provide an end mill portion, to improve cutting chip control while suppressing chipping and abrasion of a cutting edge, and to carry out stable tapping.

The cutting tool is feed-moved in synchronism with rotations by a machine tool, and machines a female thread. The cutting tool has an end mill portion, a lead-in part, and a complete thread. A peripheral cutting edge of the end mill portion is provided so as to have a diameter slightly smaller than a diameter of a male thread. An end cutting edge of the end mill portion is an even end cutting edge, has 1-5 middle-low gradients, and is provided to the extent of 50-80% of a tool diameter from the peripheral cutting edge.