Provided is a simple and easy method of producing an innoxious dry earthworm powder, while suppressing inactivation of the enzymes contained in earthworms. In the method, a homogenate obtained by grinding living earthworms is freeze-dried and the dried product is heat-treated at a temperature of 110° C. or higher but lower than 130° C. Preferably, the method according to the present invention comprises further a process for preparation of the living earthworms, which precedes the grinding step, comprising the steps of: standing the living earthworms under light for 10 to 50 hours; removing the dirt formed on the skin thereof, bringing the earthworms into contact with an organic acid for 30 seconds or less; diluting the acid with addition of water to adjust the pH of the aqueous acidic solution to a pH in the range of 2 to 5; standing the earthworm mixture under the pH condition for 3 to 180 minutes; and then washing the earthworms with water.