A pharmaceutical composition containing an artificial oxygen carrier, which has high oxygen carrying efficiency; and has a required colloid osmotic pressure, an appropriate crystalloid osmotic pressure, pH, and electrolyte balance. The composition is prepared by appropriately adding at least one substance selected from the group consisting of a compound capable of providing a colloid osmotic pressure, an electrolyte, a saccharide, an amino acid, an antioxidant, a pH adjuster, and an isotonizing agent to a preparation including a liposome-encapsulated hemoglobin in which a hemoglobin is encapsulated in a liposome or to a preparation including a conjugate of a porphyrin-iron complex and albumin.