It is an object of the invention to provide an effective technique for preventing loss of a screw fastening depth regulating member removed from a machine body in a screw fastening machine. A representative screw fastening machine includes a machine body, a motor, an input shaft, an output shaft, a first clutch element, a second clutch element, a biasing member for first and second clutch elements, a screw fastening depth regulating member. The machine body has a holding part formed in an area other than the tip end region of the machine body to removably hold the screw fastening depth regulating member. The holding part is provided such that the screw fastening depth regulating member can be attached to and removed from the holding part by utilizing elastic deformation of the holding part.