A cell transplantation device is a device for placing a cell group into a target region, which is at least one of the intradermal layer and subcutaneous layer in a living body. The cell transplantation device includes an accommodating portion that accommodates a liquid material containing the cell group； and a penetrating portion having an opening that communicates with the accommodating portion, the penetrating portion being configured to be advanced toward the target region via a skin surface of the living body so that the opening is placed at the target region. The cell transplantation device includes a substrate having a substrate surface； and a projection protruding from the substrate surface and functioning as the accommodating portion and the penetrating portion. The projection is a structure having the opening and a channel inside the projection, the channel extending from the opening.
