To provide a rotary cutting tool which is excellent in the breakage resistance and cut chip discharging property, has the small cutting resistance and can achieve accurate processing.SOLUTION: In a rotary cutting tool, a spiral cut chip discharge groove 2 heading toward a base end side from a tip of a tool body 1 is formed on the outer periphery of the tool body 1, an outer peripheral cutting edge 3 is formed on an intersection ridge line part between the rake surface of the cut chip discharge groove 2 and the outer peripheral surface of the tool body 1 or the outer peripheral rake surface formed on the outer periphery of the tool body 1, and a chip breaker groove 4 is provided so as to divide the outer peripheral cutting edge 3. The chip breaker groove 4 has the depth in a groove base end part of the chip breaker groove 4 is shallower than the depth in the groove tip part.SELECTED DRAWING: Figure 3