PURPOSE: To culture the seed fungus of mushroom, in an industrial scale, by using an agar and/or gum medium added with the extract of various additives for the cultivation of seed fungus of mushroom, a mildewcide and a surface active agent.

CONSTITUTION: A cultivation medium composed mainly of harvested saw dust is mixed with one or more components selected from the saw dust of Japanese ceder, Japanese cypress, Japanese beech or oak, soy lees, miso lees, bean cake, wheat bran, rice bran, corn cake, beer cake, powder of adlay, potato, onion, bagasse, or Sasa albo-marginata, pea, adzuki bean, and chinquapin, and the mixture is extracted by boiling in water. 100pts. wt. of the extract is mixed with 0.005W 0.02pt. wt. of a mildewcide, 2W5pts. wt. of a surface active agent for food, and proper amount of agar and/or gum to obtain an agar medium, gum medium or agar-gum medium. Spores or tissues of mushroom are inoculated in said medium and cultured.