PROBLEM TO BE SOLVED: To provide a storage duration improver and a storage duration improving method for a boiled egg that exhibit excellent bacteriostasis effect to a heat-resistant spore bearing bacterium without having adverse effects on physical properties and taste of a boiled egg.SOLUTION: There is provided a storage duration improver for a boiled egg which includes: a decaglycerin fatty acid ester (a) in which a carbon number of a constituent fatty acid is 10-14 a diglycerin fatty acid ester (b) in which a carbon number of a constituent fatty acid is 6-14 a glycerol organic acid fatty acid ester (c) ethanol (d) and water (e). There is also provided a storage duration improving method for a boiled egg which is characterized in that a boiled egg is immersed in the storage duration improver for a boiled egg that is a fluid form or a diluent of the same.
