A serum preparation apparatus is provided that can give a large amount of serum with high culture efficiency regardless of freshness of blood used. In preparing serum from blood containing at least platelets, a platelet processing step is provided in which platelet membrane in the blood is destroyed by ultrasonic treatment. After the platelet processing step, a deposition step for depositing thermolabile protein in blood and a removal step for removing the thermolabile protein, which has been deposited in the deposition step, are preferably provided.
