To provide a method for producing an alkylene oxide(AO) adduct, which enables the control of the collapse and micronization of a solid catalyst on an AO addition reaction, the maintenance of the filtration recovery of the catalyst, the recycle of the catalyst, and the production of the AO adduct at a low cost and in a state reduced in the amount of the waste catalyst.

This method for producing the alkylene oxide adduct, comprises adding the alkylene oxide to an active hydrogen-containing compound in the presence of a solid catalyst, is characterized by controlling the gas phase partial pressure of the alkylene oxide in the reaction system to 0.001 to 0.19 MPa absolute pressure.