TAPERED REAMER

To provide a tapered reamer with which it is possible to achieve an improvement in machining accuracy and machining life. In a tapered reamer 1 provided with a plurality of cutting edges 11, 12, 13 forming a helical shape on an outer circumference of a cutting edge portion having an outer diameter which increases from a tip end toward a rear end, edge-to-edge angles theta1, theta2, theta3 betweenthe cutting edges 11, 12, 13 that are adjacent to one another in the circumferential direction at the tip end differ from one another, and helix angles alpha1, alpha2, alpha3 of the plurality of cutting edges 11, 12, 13 differ from one another. Since the helix angles alpha1, alpha2, alpha3 of the unequally divided plurality of cutting edges 11, 12, 13 differ in this way, resonance during cutting can be prevented. Further, chip discharge grooves are provided between the cutting edges 11, 12, 13 that are adjacent to one another in the circumferential direction, and at least one edge-to-edge angle theta2 decreases from t