To provide a push-up floatation prevention method for a manhole, which eliminates damage and the necessity of repair by preventing a push-up floatation phenomenon, and which secures safe utilization of a carriageway, a sidewalk and the like associated with floatation.

A manhole skeleton having a cylindrical section and a bottom section is constructed by being installed with an oblique axial center, and constructed by being installed in such a manner that a floatation acting force such as hydraulic pressure directed upward from the earth is split in an oblique direction in the bottom section.