A cutter body includes cartridges 11 for allowing corresponding cutting inserts 9 to be removably fixed thereto, a cutter body member 3, second screws (cartridge fixation screws 17) for fixing the corresponding cartridges 11 to the cutter body member 3, and adjustment screws 19 for adjusting the positions of the corresponding cartridges 11, wherein a wrench reception socket 51 of each of the fastened second screws 17 and/or a wrench reception socket 50 of each of the adjustment-completed adjustment screws 19 is sealed. A rotary tool (milling cutter 1) is configured such that the cutting inserts 9 are fixed to the corresponding cartridges 11 of the cutter body.