PURPOSE: To obtain a tasty boiled frozen short-necked clam with shells preservable for a long period with hardy any sand by filtering an extract separated from the interior of the short-necked clam by boiling, completely removing impurities and then returning the extract into the shells of the clam.

CONSTITUTION: Sand is removed from a live short-necked clam and the resultant short-necked clam is washed and boiled to half-open or completely open the shells. The resultant extract of the short-necked clam is then taken out, placed in a container and then filtered to completely remove impurities such as the sand. The aforementioned boiled short-necked clam is then sunk in the obtained purified extract. The shells are closed in a state in which 100% extract is permeated in the shells. The shells are then fixed with a tool so as not to leak the extract and subsequently frozen.