The cutting tool for machining an inner surface of a hole is provided with a cutting tool main body extending in the shape of a shaft, a cutting edge portion mounted 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 formed 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 along a protruding direction at which the cutting edge portion protrudes. The opening of the coolant hole faces a direction different from the protruding direction of the cutting edge portion in the radial direction with respect to the center axis.