PURPOSE: To provide a screw tightening tool for stably holding a screw in a correct direction and absorbingly holding the screw strongly.

CONSTITUTION: A bit shaft part 3 made of an axial member and a bit part 4 exchangeably attached to this bit shaft part 3 are provided. A magnet 5 as an adsorbing member is held between the bit shaft part 3 and the bit part 4. The tip surface 4b of the bit part 4 is shaped in a form to coincide with the upper surface of a screw head part and an engaging part 4c engaged with a screw driving hole is integrally formed on the center position thereof. Thus, since the magnet is held between the bit shaft part and the bit part, a screw can be stably adsorbed and held without cracks and damages of cuts, etc., to the magnet. Also, since the upper surface of the screw head part is coincident with the bit part, the screw can be stably held in a correct direction.