PURPOSE:To economically obtain high-quality mycelial pellet of mushroom, by filling a mushroom medium in a bag, sterilizing the medium while pressing the mouth of the bag with a pressing plate, inoculating seed strain in the medium and culturing the objective mycelial pellet of mushroom. CONSTITUTION:The mouth 6 of a bag 5 filled with a mushroom medium 4 is inserted into an opening 2 of a main body A of a tool for the cultivation of mycelial pellet of mushroom. The bag 5 is squeezed to a position where the medium 4 is pressed with a doughnut-shaped pressing plate 1 and the content is sterilized. A seed strain 7 is inoculated in the medium through the mouth 6 of the bag 5, a plug B is put into the straight part 3 of the main body A and the seed is cultured for a prescribed period to obtain cultured mycelial pellet of mushroom.