The invention provides a liposome composition, which is obtained by mixing a water-miscible organic solution in which a phospholipid and cholesterol are contained in a total concentration of 100 to 200 w/v% in a water-miscible organic solvent with a first aqueous phase solution in an amount of 3/1 to 12/1 in terms of volume ratio to the water-miscible organic solution, thereby obtaining an emulsion in which the total concentration of the phospholipid and cholesterol in the resulting mixed phase is 15 to 50 w/v%, followed by subjecting the emulsion to external solution exchange with a second aqueous phase solution, wherein an ion gradient is formed between an aqueous phase in an internal region of a liposome membrane, including the first aqueous phase solution, and an aqueous phase in an external region of the liposome membrane, including the second aqueous phase solution, and a drug can be introduced in a high encapsulation amount. The invention also provides a liposome preparation which has long-lasting controlled-release properties while maintaining a clinically sufficient effective concentration and is suitable for subcutaneous administration and so on.
