PURPOSE: To provide a drill/chisel tool and a chuck capable of reducing the wear of the chuck and a tool shank in a portable tool device such as a hammer drill device, and expanding the working range of the tool device.

CONSTITUTION: A tool shank 11 is provided with a plurality of rotary entrainment grooves 13, 14, 16 arranged not opposite to each other, and at least one locking groove 12. These rotary entrainment grooves are of open shape at a free end of the tool shank so as to introduce rotary entrainment elements 23, 24, 26 in the chuck from the axial direction. The locking groove introduces a locking element 28 in the chuck from the radial direction, and an end part adjacent to the free end of the tool shank is of closed shape so as to limit the displacement in the axial direction of the tool. An additional rotary entrainment groove 15 is provided opposite to the locking groove 12 of the tool, and an additional rotary entrainment element 25 is provided opposite to the locking element 28 of the chuck.