PROBLEM TO BE SOLVED: To obtain a cleaning liquid for blood corpuscles, especially for erythrocytes, not developing any change to the blood corpuscles, or only developing a slight reduction in their qualities at most by using an aqueous solution of a gelatin. SOLUTION: This cleaning liquid for blood corpuscles is obtained by using an aqueous solution of a gelatin preferably adjusted to have especially a molecular weight range between 2000-40000, particularly between 30000-40000, and of its concentration range between 10-100 g/l, especially between 25-60 g/l, particularly between 30-55 g/l so that the solution resultantly shows essentially an isotonic colloidal osmotic pressure. Further, it is preferable to contain 2.5-7.5 mmol/l glucose, also 130-150 mmol/l Na, 3-5 mmol/l K, 1-3 mmol/l Ca and/or 0.5-1.5 mmol/l Mg as electrolytes, and citric acid, etc., as a blood coagulation preventing agent.
