PURPOSE: To easily pull up a bucket body from a shaft hole by preventing the bottom cover from operating as anchor in a shaft hole.

CONSTITUTION: An automatic soil excavating drilling bucket is equipped with a driven part 5 in which the working apaces 6 and 7 in which blade members 3 and 4 installed on a bucket body 2 are freely inserted are formed, contact arm 13 which contacts and revolves with the blade member 3 projecting from the working spaces 6 and 7 and is energized in a certain direction, and a working shaft which opens the bottom cover of the bucket body 2 when the contact arm 13 is installed and turned. On e division 8 and the other division 9 in which the blade members 3 and 4 shift in one direction and the other direction and are engaged with the driven part 5 when a driving sfaft member 1 which is connected with a kelly bar and receives a turning driving force is pushed down or pulled up are formed in the working spaces 6 and 7. A shift division in which the blade member 3 shifts so as to contact the contact arm 13 is formed between one division 8 and the other division 9. Accordingl, even if a driving shaft member 1 is inevitably revolved in the reverse direction during excavation or pulling-up by the bucket body 2, the trouble of the opening of the bottom cover is prevented.