To provide a hole expanding part cutting apparatus forming the hole expanding part, as a nearly spherical space, for filling resin which are formed on the inner wall of connection holes formed in the end of joining pieces of lumber.

The hole expanding part cutting apparatus (A) for woodwork includes: an insertion tube (1) to be inserted into connection holes; a rotor (2) that is axially supported so as to rotatably go through the inside of the insertion tube (1) and that is connected to a motor (4); a cutting blade (25) that is attached to the rotor (2) so as to be rotatable outside the insertion tube (1) by and around the center axis (241); a tip end bearing (26) that is installed to the tip end of the rotor (2) to axially support it freely rotatably; a suction tube (10) that discharges chips produced in the connection holes through the insertion tube (1); and a cutting blade operating tool (23) that makes force act on the cutting blade (25) and that rotates the cutting blade (25) at least in the range from an angle fitting inside the connection holes to an angle vertical to the rotor (2).