To ensure that a hammer can retract by a sufficient amount without interfering with a washer receiving a rear end of a coil spring, there is disclosed an impact driver having a washer receiving a rear end of a coil spring biasing a hammer of an impact mechanism to an advanced position. The washer is annular with an inner diameter larger than an inner diameter of an annular groove disposed on a rear surface of the hammer, and includes a frontward extended portion disposed at an inner circumference of the washer. Between a carrier portion of the spindle and the washer, there is disposed a positioner that positions the washer coaxially with the spindle.