The present invention provides both an impact switching function and a shaft locking function for use in an impact screwdriver. The impact screwdriver includes a housing, a motor located in the housing, a motor drive shaft driven by the motor, a hammer which can move axially and rotate around the motor drive shaft, a hammer anvil, an impact switching device and a shaft locking apparatus. The shaft locking apparatus has a mating member coupled with the hammer anvil, an engagement ring fixed to the housing and a middle member located between the mating member and the engagement ring. The shaft locking apparatus has a locked position, where the mating member is secured to the hammer anvil and also secured to the engagement ring and the housing.