Abstract: A fastener driving device includes a body, a driver guide extending downwardly from the body for driving fasteners by a driver, a first abutting member mounted on the driver guide and having a first reference surface for abutment on an edge of a work to be fixed, and a second abutting member having a second reference surface for abutment on an edge of another work which has been previously fixed. An adjusting mechanism is provided for adjusting the position of the second abutting member relative to the first abutting member. The adjusting mechanism includes a support member mounted on the body and supporting the second abutting member in such a manner that the second abutting member is slidably movable along a direction substantially perpendicular to a longitudinal direction of the driver guide. A tightening mechanism is operable for fixing the position of the second abutting member and for permitting movement of the second abutting member.