To simply, efficiently, repetitively, continuously and surely grow a large amount of Volvariella speciosa sing. var. volvacea even by anyone.

Straws 8 supplied with sufficient water are spread to a prescribed thickness over a base 7 placed in a room where temperature and humidity can be regulated and a culture medium material 9 is laid on the straws 8 to form a mushroom bed 10, which is then sterilized. A spawn is subsequently inoculated and the mushroom bed 10 is kept warm at a prescribed temperature and humidified to ≥70% humidity. After a primordium is formed, the temperature is then reduced to a lower temperature than that at which the mushroom bed 10 is kept warm by a prescribed temperature to form a fruit body.