To provide a screw and a screwdriver capable of tightening and fixing by a strong tightening force without damaging a groove.

This screw 10 has a head 20, a screw shaft 30 projecting out of the reverse surface of the head 20 and having a screw 31 formed at an outer circumference. The groove 21 in which the tip 52 of the screwdriver 50 is inserted is formed on the surface of the head 20. An inner surface 25 positioned in the tightening rotation direction of the screwdriver 50 of the groove 21 is formed into a surface roughly parallel with the axial direction of the screw shaft 30. An inner surface 27 positioned at the reverse side of the tightening rotation direction of the screwdriver 50 of the groove 21 is formed into a tapered surface inclined toward the top from the bottom of the groove 21 to make an opening gradually expand.