Provided is a method of producing a dry earthworm powder without deterioration in useful pharmacological action, by removing dirt on the skin of earthworms while allowing the earthworms to excrete the digest remaining in the digestive tracts efficiently without weakening the earthworms, which comprises the steps of: standing living earthworms under light for 10 to 50 hours, removing the dirt formed on the skin thereof, adding an organic acid to the living earthworms, diluting the acid rapidly with addition of water, adjusting the pH of the aqueous acidic solution to 2 to 5, standing the earthworm mixture for 3 to 180 minutes under the pH condition, washing the earthworms with water, grinding the earthworms into a homogenate, freezing the homogenate at -18.degree. C to -35.degree.0 C, keeping the frozen homogenate for 20 to 240 hours, and freeze-drying and degassing the frozen homogenate under vacuum simultaneously.