Using a bubble column fermentor, submerged culture of Agaricus blazei mycelium was carried out to find the potential for large-scale culture by bubble column fermentors. Round pellets of A. blazei mycelium of 5 mm to 20 mm in diameter were found in the fermentor. The optimum conditions on pH, cultivation temperature, compositions of nitrogen and carbon sources, and aeration rate were obtained, where the cell concentration and the overall growth rate maximum.