There is provided a method for noninvasively evaluating the cell state (proliferation, multi-layering, and differentiation) of a cell sheet as a mimic tissue at the time of culturing the cell sheet. The method is characterized in that an analysis of an amino acid is conducted with the use of the culture supernatant of a cell sheet to monitor a change in the concentration of any amino acid selected from a group of 5-species of amino acids (Ile, Val, Ser, Leu, and Ala), thereby making a determination.