A dust collecting device (140; 170) that is adapted to be attached to a tool body of an impact tool to which different lengths of tool bits are selectively coupled and is adapted to collect dust generated by the impact tool in which the tool bit detachably coupled to a front end region of the tool body is caused to rectilinearly move in an axial direction of the tool bit, comprising: a dust suction port (141a; 172) through which dust is sucked up and which can be adjusted in position in the axial direction of the tool bit according to a length of the selectively coupled tool bit among the tool bits of different lengths in the axial direction, a dust collecting part having the dust suction port at its front end, and a dust transfer part which is connected to the dust collecting part in order to transfer dust downstream from the dust suction port, wherein the position of the dust suction port can be adjusted in the axial direction of the tool bit by changing a mounting position of the dust transfer part with respect to the tool body, and wherein the dust transfer part comprises a dust collecting hose which extends in the axial direction of the tool bit and has a bellows-like part formed at least in part of the dust collecting hose, characterized in that the dust collecting device further comprises a hose holding part (147; 161) which can be mounted to the tool body and engaged with the bellows-like part, the hose holding part (147; 161) has one or more projections (148b; 164b), and the dust collecting hose is held by the hose holding part by engagement between the one or more projections of the hose holding part (147; 161) and a valley of the bellows-like part of the dust collecting hose, wherein the position of the dust suction port can be adjusted by changing an engagement position of the bellows-like part in an axial direction with respect to the hose holding part (147; 161). a dust suction port (141a; 172) through which dust is sucked up and which can be adjusted in position in the axial direction of the tool bit according to a length of the selectively coupled tool bit among the tool bits of different lengths in the axial direction, a dust collecting part having the dust suction port at its front end, and a dust transfer part which is connected to the dust collecting part in order to transfer dust downstream from the dust suction port, wherein the position of the dust suction port can be adjusted in the axial direction of the tool bit by changing a mounting position of the dust transfer part with respect to the tool body, and wherein the dust transfer part comprises a dust collecting hose which extends in the axial direction of the tool bit and has a bellows-like part formed at least in part of the dust collecting hose, characterized in that the dust collecting device further comprises a hose holding part (147; 161) which can be mounted to the tool body and engaged with the bellows-like part, the hose holding part (147; 161) has one or more projections (148b; 164b), and the dust collecting hose is held by the hose holding part by engagement between the one or more projections of the hose holding part (147; 161) and a valley of the bellows-like part of the dust collecting hose, wherein the position of the dust suction port can be adjusted by changing an engagement position of the bellows-like part in an axial direction with respect to the hose holding part (147; 161).