This invention relates to a method for screening for a growth-promoting factor for pluripotent stem cells with a conditioned medium which is generated by culturing feeder cells in a serum-free medium that contains L-ascorbic acid, insulin, transferrin, selenium, and sodium bicarbonate and does not contain a serum nor serum replacement; a method for growing pluripotent stem cells via feeder-free culture using the conditioned medium; and a method for growing pluripotent stem cells by carrying out feeder-free culture of pluripotent stem cells cultured in advance on feeder cells in the serum-free medium.