To provide a bioreactor capable of performing a culture using different fluid media on both surfaces of an animal cell cultured product, reproducing shearing by the blood and material feed in the medium in contact with the animal cells, thus enabling the cells to be cultured in the state of no cell layer debonding under conditions close to those of living body.

The bioreactor has such a structure that there is at least one polymeric hydrous gel membrane for making the animal cells adhere to at least one surface of the membrane and different fluids can be made to flow respectively on one side of the polymeric hydrous gel membrane and the other side.