To turn a device at a narrow turning radius by providing an excavat ing machine main body with a turning support base, and fitting a boom to this turning support base freely to be stood and fallen.

In hoisting a cylindrical casing 34 from a load carrying platform of a motor truck 51 so as to move it to an upper part of a vertical shaft 53, a boom 6 is turned, risen and fallen at this side of the vertical shaft 53. At the time of discharging the soil inside of the cylindrical casing 34 with a bucket 25, the boom 6 is turned, risen and fallen at a back side of the vertical shaft 53. At the time of transferring to the hoisting work of the bucket 35 after finishing the cylindrical casing 34 hosting work, or at the time of returning to the hoisting work and the soil discharging work, the boom 6 is turned, and the boom is turned around a turn support base 7 in any case of the hoisting work and the soil discharging work, and an excavating machine main body 4 is not turned. Turn is performed at the minimum radius, and the vertical shaft excavating work in a narrow space and a narrow road can be smoothly performed.