Abstract: Provided are a method for producing undifferentiated cell spheroids, the method comprising the step of culturing undifferentiated cells on a cell-adhesive surface of a cell culture sheet; a method for maintaining cell spheroids in an undifferentiated state, the method comprising the step of culturing undifferentiated cell spheroids on a cell-adhesive surface of a cell culture sheet; and a cell spheroid obtained by the method.

Abstract: The present invention provides a cell culture sheet comprising a plurality of recesses each having an opening of 1000 ?m or less in diameter, wherein each recess has an inner circumferential face and a bottom face, wherein the inner circumferential face has a non-cell adhesive surface, and wherein the bottom face has a cell-adhesive surface; and a method for producing a cell culture sheet, the method comprising laminating of a layer having a non-cell adhesive surface and a layer having a cell-adhesive surface, wherein the layer having a non-cell adhesive surface has a plurality of through-holes of 1000 ?m or less in diameter. The cell culture sheet of the present invention can be prepared simply and assists efficient cell culture operation, and therefore can preferably be used in the field of cell-based pharmaceutical preparations, for example, spheroid-containing pharmaceutical preparations etc.