PURPOSE: To make it possible to carry out dissolved gas control accurately, by effecting mutual transfer of culture solution inside and outside of a hollow fiber while making pressure of the culture solution inside the fiber constant by pressurization and decompression of the solution in the outside space by a pump communicated with the outside space of the fiber.

CONSTITUTION: In a hollow fiber cartridge 80, a culture solution is fed to the inside of a hollow fiber, the culture solution is set in the outside of the fiber and biological cells are multiplied in the outside of the fiber while mutually transporting the culture solutions inside and outside of the fiber through the fiber. Then the mutual transfer of the culture solutions in the inside and outside of the fiber is carried out while making pressure of the culture solution inside the fiber substantially constant by pressurization and decompression of the solution in the outside space of the fiber by a pump 1 communicated with outside space ECS of the fiber. Consequently, dissolved gas composition, change in pH value and oxygen consumption ratio caused by multiplication and metabolism of cell can be precisely carried out and dissolved gas can be accurately controlled.