A cutting tool for machining an inner circumferential surface of a hole formed on a workpiece, comprising: a cutting tool main body extending in the shape of a shaft; a cutting edge portion which is provided on a head portion of the cutting tool main body so as to radially-outwardly protrude with respect to the center axis of the cutting tool main body; and a coolant hole which is provided at the cutting tool main body along the center axis of the cutting tool main body, wherein the cutting edge portion is a groove-forming cutting edge portion for forming an annular groove at the center of the rotating axis on an inner circumferential surface of the hole formed on the workpiece, characterized in that: the coolant hole is bifurcated into a first coolant hole and a second coolant hole extending to the opposite direction of the first coolant hole, the first coolant hole provided at the cutting tool main body so as to have an opening at a position apart from the cutting edge portion on a circumferential surface of the head portion of the cutting tool main body, thereby flushing out a coolant from the opening to an axially orthogonal plane orthogonal to the center axis and also in a protruding direction at which the cutting edge portion protrudes; wherein the opening of the first coolant hole faces a direction different from the protruding direction of the cutting edge portion in a radial direction with respect to the center axis. a cutting tool main body extending in the shape of a shaft; a cutting edge portion which is provided on a head portion of the cutting tool main body so as to radially-outwardly protrude with respect to the center axis of the cutting tool main body; and a coolant hole which is provided at the cutting tool main body along the center axis of the cutting tool main body, wherein the cutting edge portion is a groove-forming cutting edge portion for forming an annular groove at the center of the rotating axis on an inner circumferential surface of the hole formed on the workpiece, characterized in that: the coolant hole is bifurcated into a first coolant hole and a second coolant hole extending to the opposite direction of the first coolant hole, the first coolant hole provided at the cutting tool main body so as to have an opening at a position apart from the cutting edge portion on a circumferential surface of the head portion of the cutting tool main body, thereby flushing out a coolant from the opening to an axially orthogonal plane orthogonal to the center axis and also in a protruding direction at which the cutting edge portion protrudes; wherein the opening of the first coolant hole faces a direction different from the protruding direction of the cutting edge portion in a radial direction with respect to the center axis. the coolant hole is bifurcated into a first coolant hole and a second coolant hole extending to the opposite direction of the first coolant hole, the first coolant hole provided at the cutting tool main body so as to have an opening at a position apart from the cutting edge portion on a circumferential surface of the head portion of the cutting tool main body, thereby flushing out a coolant from the opening to an axially orthogonal plane orthogonal to the center axis and also in a protruding direction at which the cutting edge portion protrudes; wherein the opening of the first coolant hole faces a direction different from the protruding direction of the cutting edge portion in a radial direction with respect to the center axis.