To simplify installation performance of a tension spring for returning a movable cover, by overcoming the problem wherein the tension spring is conventionally fixed to the blade case side with a fixing screw and is troublesome in installation work, in a fixation on the other end side of the tension spring for energizing the movable cover for opening-closing a lower end of a rotary blade tool projected to the base under surface side to the closing side, in a cutting tool for supporting a tool body on a base placed on a cutting material.

This cutting tool is configured to pull-hook the other end side 45b of the tension spring 45 on a spring pulling-hooking shaft part 46 having the positioning function of one case body 13b and the other case cover 13a, by forming a blade case 13 for covering the upper side of the rotary blade tool as a half-split structure.