To enable transport by reducing a machine width of a shaft boring machine, by dividing a circular casing, fastening joining of the divided part by a vertical bolt perpendicular to the shell surface, or fastening the joining by a horizontal bolt parallel to the shell surface.

For example, respective casings 1, 2 of a first stage and a second stage are divided into three parts in the vertical direction, and a welded butting plate 5 is arranged on one side of a vertically divided shell 3 to be fastened by the adjacent shell 3 and a vertical bolt 4. In this case, a ring plate 6 is welded to the upper part of the first stage casing 1 to be fitted to the skirt part of the second stage casing 2 so that both are fastened by a connecting bolt 7. Therefore, a circular casing having a large diameter not less than a vehicle width of a trailer is divided, and is transported by the trailer to be easily assembled on the spot. Therefore, a circular shaft having a diameter not less than a trailer width can be constructured, and the casings optimal for a shaft construction method by a field corrugated steel pipe of a thin steel plate having a large diameter can be formed.