An artificial organ is disclosed which has a film of either fat-soluble vitamin or a mixture of fat-soluble vitamin with glycerin deposited on the surfaces of parts of the artificial organ susceptible to contact with body fluid under treatment in a zone for flow of the body fluid within the artificial organ. Also disclosed is a sterilized artificial organ which has the aforementioned coat further subjected to contact with a physiologically parmless liquid and then to a treatment for sterilization.