The disclosure provides a method of freezing an aggregate of pluripotent stem cell-derived cardiomyocytes, comprising: (i) immersing an aggregate of pluripotent stem cell-derived cardiomyocytes in a cryoprotective solution; and (ii) freezing the aggregate immersed in the cryoprotective solution. The disclosure also provides a frozen aggregate of pluripotent stem cell-derived cardiomyocytes frozen by the method.