A fastening device includes a rotational drive portion that rotationally drives a socket, an advance/retract drive portion that causes this socket to advance or retract along a rotational axis thereof, a magazine that retains a plurality of heads that retain bolts, and a switching portion that moves this magazine to selectively position one of a plurality of heads ahead and on the rotational axis of the socket. One of the heads is selected and positioned on the rotational axis of the socket by the switching portion, then the socket is advanced by the advance/retract drive portion and the head thus selected is retained by the socket, then the socket is advanced further by the advance/retract drive portion and the head to detach is detached from the magazine, and then the head is rotated by driving the rotational drive portion, thereby fastening a bolt retained in the head.