To provide a screw (including a small bolt) with a (plane, dish, round, etc.) head capable of easily screwing an article to a member with an appropriate twisting torque, and to provided a screwdriver therefor.

A tilting slot 3 is provided to form a recessed cross section of a groove notched in a head surface 20 of the screw S with a head, to form a plane shape thereof into minus (-), plus (+) and three-pronged shape (Y), to form a projection in the center thereof, and to form cross section on one side of the center line into a nearly inverted V. A core part 6 of a tip blade part 50 of the screwdriver D to be engaged with each of the tilting slots 3 (-, +, Y) is cut to form a recessed part, and the screw S with a head is accurately screwed or loosened to/from the member by a blade tip part (bit) 5 formed with a nearly inverted V in cross section thereof on one side of the center line (similarly with the tilting slot).