PURPOSE: To proliferate and maintain animal cells by culture in a large amount while avoiding any type of damages caused by environment in vitro by using a culture solution to which a blood dialysate or an ultrafiltrate from a bovine blood is added.

CONSTITUTION: (i) A tissue or an organ explant, (ii) a primary, a secondary, a tertiary or a following cell culture product, (iii) a diploid, a heteroploid or an aneuploid cell strain or cell system or (iv) an optionally transformed permanent a cell system which has characteristics of growing in an attached state or unattached state in an conventional medium or a specific medium is proliferated and maintained by cell culture in a large amount by using a medium comprising ≥0.5vol.%, preferably 0.5-4vol.% of a blood dialysate or an ultrafiltrate containing neither a macromolecular nor a component having ≤10,000 molecular weight from a bovine blood.