To smoothly perform supplementary lifting work following excavating work, accurately and safely execute excavation by sufficiently supporting reaction force of excavation, and simplify a structure.

Each base end of a front frame 38, a derricking cylinder 40, and a latticed boom 32 is rotatably attached on each different fulcrum of a base machine main body 31. The base end of the front frame 38 is supported by the base machine main body 31 between each base end of the latticed boom 32 and the derricking cylinder 40, and the base end of the derricking cylinder 40 is supported by the base machine main body 31 on the ground side from the base end of the front frame 38. Moreover, the front frame 38 is supported by the derricking cylinder 40 is such state that its axial direction is crossed to an extending direction of the front frame 38, and a supporting end 40a of the front frame of the derricking cylinder 40 is provided on a side opposed to the ground side of the front frame 38, in other wards, a back side of the front frame 38.