A powder-actuated fastener-driving tool includes a barrel unit inserted movably into a housing, a holder disposed movably in the housing, abutting against the barrel unit and having a through hole defined by an inner annular surface, and a spring-loaded firing pin disposed fixedly in the housing, having a free end portion extending into the through hole in the holder, and movable among normal and standby positions, where the firing pin is inclined due to engagement between the free end portion thereof and the shoulder portion of the holder, and a firing position. When a trigger unit mounted on the housing is operated to switch the firing pin from the standby position to the firing position, the free end portion of the firing pin disengages the shoulder portion of the holder to move frontwardly to thereby contact and ignite gunpowder in a chamber in a rear end portion of the barrel unit.