An air-driven rotary cutting tool including a grip part, a head part provided at a distal end of the grip portion, and a rotor of double-wheel type rotatably installed in a hollow portion formed in the head part. The rotor has a first turbine blade portion provided with a plurality of first turbine vanes surrounding the rotary axis and a second turbine blade portion integrally formed with the first turbine blade and having a plurality of second turbine vanes surrounding the rotary axis. The first turbine vane has, on its side when seen in a direction into the rotary axis, a concave shape concaved in a direction of rotation of the rotor, and the second turbine vane has, on its side, a concave shape concaving in a direction opposite from the first turbine vane.
