PROBLEM TO BE SOLVED: To provide an alkylene oxide adduct having good fluidity and storage stability at low temperature and excellent emulsifying power and thickening performance, and to provide a production method of the adduct.SOLUTION: The production method of an alkylene oxide adduct includes a step of simultaneously supplying ethylene oxide and propylene oxide to alcohol to effect an addition reaction. When the supply starting time T0, supply finishing time T100, and T1 and T2 between T0 and T100 are defined to satisfy the relationship of T0
