A fastener assembly comprises a stud bolt including a bolt portion and a weld end to be welded to a workpiece, and a nut member to be screwed into the stud bolt. The nut member screwed into the stud bolt before welding is formed out of an electrically conductive material to allow the welding current to flow through the nut member into the stud bolt and weld the nut member to the workpiece while connected to the stud bolt. Then an attachment member is disposed on top of the workpiece, and the attachment member is fastened to the workpiece when the nut member is turned in the fastening direction.