Provided is a fat emulsion containing a prostaglandin which has improved stability of prostaglandin excellent emulsion stability excellent transparency and long storage life. A fat emulsion which has a pH of 4.5 6.0 and contains a prostaglandin an oil component lecithin in an amount of 0.15 times the mass of the oil component a water soluble acid having a dissociative group with a pKa of 4.0 6.0 or a salt thereof and water. A fat emulsion which contains a prostaglandin an oil component lecithin in an amount of 500 5 000 times the mass of the prostaglandin contained therein and 0.5 10 times the mass of the oil component contained therein and water. This fat emulsion also contains a higher fatty acid in an amount of 0.06 times the mass of the lecithin contained therein.
