Problem to be solved. To provide an emulsifier which can stably maintain emulsified state of an emulsion in which oil droplets are dispersed in a solution, and an emulsification maintenance method, and an emulsion containing the emulsifier. Solution. An emulsified state of an emulsion can be stably maintained by an emulsifier containing a surfactant and an animal fat and oil. In the meantime, when the surfactant is animal-derived lecithin, the animal fat and oil, which is 1 to 20 times an amount of the animal-derived lecithin by mass ratio, is preferably contained, and the animal fat and oil, which is 1.5 to 10 times the amount of the animal-derived lecithin by mass ratio, is further preferably contained.