A fat emulsion comprises a prostaglandin as an active ingredient, the fat emulsion comprising a phospholipid that comprises phosphatidylcholine (PC) and phosphatidylglycerol (PG) and has a ratio of PC to PG (PC:PG) of 85:15 to 99.7:0.3.本發明之以前列腺素為有效成分之脂肪乳劑,係含有含磷脂醯膽鹼(PC)以及磷脂醯甘油(PG)之磷脂質,且該磷脂質中PC與PG之比(PC:PG)為85:15~99.7:0.3。