PURPOSE: To make any drop in machining operation efficiency to a work ascribed to a shortage of supply for a working fluid so as to be obviatable.

CONSTITUTION: A working fluid feeding means 10, discharging a working fluid toward a cutting part 2B of a rotary working tool 2, is installed in a working head 3 supporting the rotary working tool 2 in a mode that this feeding means 10 is tilted to some extent to give a timing advance to the side of a rotational direction of the tool 2 in relation to a center axis of this tool 2. In addition, simultaneously with this, a clamper side working fluid feeding means 20, feeding the inner part of a work hole Wa in a workpiece W with a working fluid 100, is installed in a clamper pressing and holding this workpiece W.