A recess surface portion 123 is formed in a predetermined range L1 from a front end 103 toward a rear end, of a lateral flank 120 of a front end portion 102 of a holder 100, so as to be recessed relative to a lateral flank 120b of a rear portion 122, a circular arc surface portion (frontward-facing surface) 125 formed in a circular arc shape as seen from a rake face 105 side is provided on the rear of the recess surface portion 123, and an ejection port 150 is opened in the frontward-facing surface. Accordingly, supply of the coolant at the lateral flank side is ensured, and cutting can be performed at a position closer to a chuck Ck due to no protruding portion being present at the lateral flank side of the holder as in the conventional art.