The present invention provides: a method of producing a cell sheet, comprising the steps of (1) seeding retinal pigment epithelial cells onto a collagen gel and culturing the retinal pigment epithelial cells on the collagen gel to thereby form a cell sheet composed of the retinal pigment epithelial cells and (2) decomposing the collagen gel with a collagenase to remove the cell sheet composed of the retinal pigment epithelial cells; and others.