Method for producing alkoxylated compound

(57) [Summary] [PROBLEMS] Even when a reaction solution having a high viscosity is used, Provided is a method for efficiently adding an alkylene oxide to an active hydrogen-containing compound. SOLUTION: When adding an alkylene oxide to an active hydrogen-containing compound, the viscosity of the reaction solution is 10 mP. In the case of a · s or more, the following formula (1) is obtained by rotation of a blade continuously provided in the stirring reactor in the vertical direction. (Where A is the length (m) of the blade newly immersed by the supply of the alkylene oxide, h 1 is the liquid level before supply of the alkylene oxide (m), and h 2 is the supply of the alkylene oxide. The liquid is stirred so that the numerical value C expressed by the liquid level height (m) becomes 0.5 or more.