A fastener guide mechanism in a fastener driving tool includes a door member for closing an opening formed on one of the lateral sides of a fastener guide having a driver guide and a fastener guide. The fastener guide includes therein a fastener guide channel. A fastener feeding device having a fastener feeding member moves the fasteners connected by a carrier and disposed in the fastener guide channel forwardly toward the driver guide track of the driver guide one after another. A pressing member is mounted on the door member for pressing the connected fasteners on the fastener feeding member. The pressing member is operable to contact the connected fasteners at a first position when the connected fasteners are of a first kind. The pressing member is operable to contact the connected fasteners at a second position separated from the first position in a direction away from the fastener guide channel. The pressing member is biased by a biasing member for normally biasing toward the connected fasteners. A stopper member prevents movement of the pressing member from the first position in a direction away from the fastener guide channel.