Entrapment of bovine serum albumin into microcapsule using polylactic acid as a wall material was carried out by solvent evaporation of a W/O/W emulsion prepared by a two-step emulsification method. Effects of the conditions ill the first step emulsification, which gave a W/O emulsion, and the concentrations of additives in the inner and outer aqueous phases on the entrapment efficiency and the morphology of the microcapsule are discussed. The entrapment efficiency of albumin decreases with increasing in the hold up of dispersion phase in the first step W/O emulsion preparation, and the concentration of additives in the inner aqueous phase. On the other hand, by ultrasonic treatment for W/O emulsion and an increase in the concentration of additives in the outer aqueous phase, entrapment efficiency of the protein increases. Permeation of water from the outer into the inner aqueous phase by osmotic pressure difference, which causes the coalescence of the inner aqueous phase droplets and a decrease in the capsule wall thickness, decreases the entrapment efficiency. By considering these factors, almost all the amount of albumin dissolved in the inner aqueous phase can be entrapped in the capsule, and it is possible to control the entrapment of water soluble core materials in the preparation of microcapsules by the solvent evaporation method.