To perform a highly efficient and low-cost excavation work dispensing with a large-scale crane truck necessary for installing and supporting a drill, its carry-in, its installation, and its carry-out, and saving a space in an excavator applied in executing foundation pile work and temporary earth retaining work.

This screw rod excavator comprises a drill hoisting winch 2-1 in installed in a rotary table machine body 1 and excavating, a drill installation winch 2-2, a support structure 3, the screw rod 5, a screw rod guide 6, and a screw rod guide support member 7, and is so constituted that a power is transmitted to a sprocket 9 in the screw rod guide side via a chain 11 by the rotation of a drive side sprocket 10 and rotate the sprocket 9. When the outside diameter dimension of the screw rod is changed, it can be corresponded by using a screw rod guide 6 of an appropriate dimension.