According to the process of the present invention for preparing a pasty proteinous material or a protein­ous food, crustaceans are boiled and milled under suf­ficient conditions for inactivating enzymes contained therein and then proteolytic enzyme(s) and/or micro­organism(s) are allowed to act thereon. Thus various protein sources including crustacean meat remaining in the trunks and carapaces, which have been disposed hitherto, can be efficiently utilized.