The present invention provides a screw, comprising a screw head having a drive recess and a screw shank having threads and being integrally formed with the screw head, wherein the drive recess includes a plurality of engaging grooves equiangularly radiating from an axis of the screw in plan view, a bottom face of each engaging groove having a steep slope, which is near to the screw shank, and a gentle slope, which is far from the screw shank, for enlarging the engaging area of the engaging grooves.