A polymer that changes hydration at a temperature between 0 to 80°C is coated on the surface of a cell culture support, and islet cells are cultured on the support at a temperature range that causes polymer to have weak hydration, then the temperature of a culture solution is changed to a temperature that causes the polymer to have strong hydration to obtain islet cells in a sheet form. Such islet cells in a sheet form have an insulin producing function even if there is no blood flow.
