Impact tool

A representative impact tool includes a bit holding device 104 that includes an elongate tool holder 151 having a bit holding hole 151 a into which a tool bit 119 is removably inserted, an outer shell component 159 which forms an outer shell of the bit holding device 104 and is mounted onto a front end portion of the tool holder 151 by moving it from the front end of the tool holder 151 toward the tool body, a stopper 171 which is fitted onto the tool holder 151 such that it is prevented from moving in a longitudinal direction of the tool holder, and serves to prevent the outer shell component 159 from becoming detached from the front end of the tool holder 151, and an opening prevention member 175 which is disposed outward of a center position of the stopper 171 in the longitudinal direction of the tool holder 151 and opposed to an outer surface of the stopper 171 in a direction transverse to the longitudinal direction of the tool holder, and prevents the stopper 171 from opening in the direction transverse to the longitudinal direction of the tool holder.