To bore a pit hole with a firm pit peripheral-wall, in which there is no possibility of collapse, easily in a ground surely while realizing complete earth no-removal in the boring construction method and device of the foundation ground.

A pre-excavation edge 2 is formed to the lower section of the front end of an auger head so that an auger lever 4, in which several resistance pieces 5, 5 having constant length and edge width in the axial direction are annexed alternately on a shaft peripheral surface at mutually different spatial places at proper intervals, is connected detachably on the upper same shaft of an excavator 1, in which a screw edge piece 3 is arranged in parallel on the upper section of the pre-excavation edge 2, through a connecting washer 6.