PURPOSE: To perform the bit detach operation in a short time by connecting a bit and a chuck by a spline and a groove, and inserting a segment pushup tool to detach the bit where a segment of a chuck is engaged.

CONSTITUTION: A quick detach bit device 10 is formed by an abrasion sleeve 12, a chuck 14, and a bit 16. Subsequently, a recessed part 48 is provided in the end 28 of the chuck 14, a segment 50 is put in and out from the recessed part 48 and an elastic O ring 56 is engaged with the segment 50 to push the segment 50 inward the inner peripheral surface 34. Subsequently, plural splines 58 and the grooves 60 are provided in the inner peripheral surface 34 of the chuck 14, and a spline 70 and a groove 72 are formed in the outer peripheral surface 68 of the bit 16. The bit 16 inserted in the chuck 14 is detached by inserting a quick release tool 78 into a tool go in-and-out groove 72a. Thus, bit detach can be quickened.