A sheet-shaped cell culture is disclosed that includes myocardial cells derived from pluripotent stem cells and has excellent functional properties. A sheet-shaped cell culture obtained by culturing a cell population that includes myocardial cells derived from pluripotent stem cells, wherein the proportion of the number of the myocardial cells derived from pluripotent stem cells to the total number of cells in the cell population is 50% to 70%; a method of producing the sheet-shaped cell culture; a composition including the sheet-shaped cell culture; and a method of treating a disease using the sheet-shaped cell culture or the composition.