There is provided a fat emulsion which has a pH of 4.5 to 6.0 and includes a prostaglandin compound, an oil ingredient, a lecithin, the content of which is 0.15 times or more by mass the content of the oil ingredient, a water-soluble acid having a pKa of 4.0 to 6.0 and having a dissociable group or a salt thereof, and water； and a fat emulsion which includes a prostaglandin compound, an oil ingredient, a lecithin, the content of which is 500 to 5,000 times by mass the content of the prostaglandin compound and is 0.5 to 10 times by mass the content of the oil ingredient, and water, and in which the content of a higher fatty acid is 0.06 times or less by mass the content of the lecithin.
