PURPOSE: To obtain a hemoglobin-containing liposome useful as a artificial blood capable of exhibiting suppression effects stable for a long period to oxidation with passage of time of hemoglobin by sealing electron donor and electron transfer body necessary in reduction of hemoglobin and methemoglobin in the interior of liposome.

CONSTITUTION: An aqueous solution containing hemoglobin, electron donor such as pyridine nucleotide coenzymes (e.g. β-nicotinamidoadeninedinucleotide) and electron transfer body (preferably methylene blue) having action capable of receiving electron from the electron donor and reducing methemoglobin to hemoglobin is sealed from bimolecular membrane of lipid into the interior of liposome. An amount of the electron donor added is 0.5-10, preferably 0.5-3, expressed in terms of weight molar ratio and concentration of the electron transfer body in an aqueous solution is 0.1×10-10 to 1μM, preferably 0.1×10-10 to 0.1μM.