PURPOSE: To uniformize the concentration of components necessary for cell proliferation in a medium and to culture cells without making the cells in a overcrowded state by culturing the cells in a cell incubator using specific hollow yarn while circulating a cell floating solution.

CONSTITUTION: A cell floating solution is circulated (preferably 30m$1/minute) through a dispersing bundle of hollow yarn of a cell incubator equipped with a conduit wherein both end parts of the dispersing bundle (5,000-15,000 filaments are packed into a shell) of hollow yarn (comprising cellulose or cellulose diacetate) having permeability to nutrient of cells but no permeability to cells, having 100-300μm inner diameter, 10-20μm film thickness and 100-200mm length) are fixed so as to make both the end parts open to the outside of a container. The incubator is furnished with two conduits communicating with a dispersing gap part of the hollow yarn. A culture solution necessary for cell proliferation is circulated (preferably 5-15m$1/minute) through the dispersing gap part to culture cells.