PURPOSE: To produce the liposome having stability in vivo with good reproducibility by mixing an aqueous solution contg. a substance which is contained within the space of a membrane to the acyl glycerol solution of a substance to be contained in a membrane component substance and a membrane structural substance.

CONSTITUTION: The substance to be contained in the membrane component substance and the membrane structural substance is dissolved to a small amount of acylglycerol and/or a higher fatty acid to form the acylglycerol solution. Said acylglycerol solution is mixed to a small amount of the aqueous solution which contains the substance to be contained within the space surrounded by the membrance of a microspore and has pH of 4W10 followed by emulsifying the obtd. solution at a temp. of 15W65°C and in the atmosphere of nitrogen gas. The stable obtd. emulsion is added to a large volume of the prescribed aqueous solution so as to maintain pH of the aqueous solution to 4W10, while agitating it to produce liposome.