A rotary cutting tool in which: a first cutting-chip discharge groove disposed from a tool tip towards a base-end side is formed on an outer periphery of a tool body; a plurality of second cutting-chip discharge grooves, provided along a spiral disposed from the tool tip towards the base-end side so as to intersect with the first cutting-chip discharge groove, are formed on an outer periphery section of the tool body where the first cutting-chip discharge groove is absent; a base-end-side outer periphery cutting edge is formed on an intersection ridge between a rake face of a second cutting-chip discharge groove, which faces a direction of tool rotation, and an outer peripheral surface of the tool body or an outer peripheral relief face formed on the outer periphery of the tool body; wherein an end cutting edge is provided at a tip section of the tool body; a tip-side outer periphery cutting edge is formed on an intersection ridge between the rake face at a tip section of the first cutting-chip discharge groove and an outer peripheral surface of the tip of the tool body or an outer periphery relief face formed on an outer periphery of the tip of the tool body; and the base-end-side outer periphery cutting edge is provided further towards the tool base-end side than the tip-side outer periphery cutting edge characterized in that: the first cutting-chip discharge groove is provided as a leftward spiral having a spiral angle that is smaller than the spiral angle of the second cutting-chip discharge grooves minus 10°, disposed from the tool tip to the base-end side; the second cutting-chip discharge grooves are provided as a leftward spiral; the spiral angle of the second cutting-chip discharge grooves is set to at least 50° and less than 90°; the occupancy angle of the first cutting-chip discharge groove in cross-section perpendicular to a tool axis is equal to or greater than 15° and smaller than 360 divided by the number of second cutting-chip discharge grooves present; and the base-end-side outer periphery cutting edge is provided so that the number of effective teeth at an arbitrary point in a direction of tool axis is no less than /the number of the second cutting-chip discharge grooves minus the number of the first cutting-chip discharge groove. the first cutting-chip discharge groove is provided as a leftward spiral having a spiral angle that is smaller than the spiral angle of the second cutting-chip discharge grooves minus 10°, disposed from the tool tip to the base-end side; the second cutting-chip discharge grooves are provided as a leftward spiral; the spiral angle of the second cutting-chip discharge grooves is set to at least 50° and less than 90°; the occupancy angle of the first cutting-chip discharge groove in cross-section perpendicular to a tool axis is equal to or greater than 15° and smaller than 360 divided by the number of second cutting-chip discharge grooves present; and the base-end-side outer periphery cutting edge is provided so that the number of effective teeth at an arbitrary point in a direction of tool axis is no less than /the number of the second cutting-chip discharge grooves minus the number of the first cutting-chip discharge groove.