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.本發明係提供簡便地、能夠抑制蚯蚓中所含有酵素活性的失活、並使其無害化的蚯蚓乾燥粉末的製造方法。本發明的蚯蚓乾燥粉末的製造方法為將活蚯蚓粉碎成為粉碎物，並將其冷凍乾燥，其特徵在於在110℃以上，低於130℃的溫度下對得到的乾燥物進行加熱處理。上述活蚯蚓較佳為使用下述的活蚯蚓：將活蚯蚓放置于明亮場所10~50小時後，將附著在表皮上的污染物剝離，接下來使其與有機酸接觸，並盡可能快速地用水稀釋並將pH調整到2~5，在該條件下保持3~180分鐘後，經水洗後的活蚯蚓。
