PURPOSE: To economically obtain the title compound in controlled particle size of a catalyst by suspending lithium phosphate having a specific particle size distribution as the catalyst in an organic solvent having high boiling point in isomerization of propylene oxide.

CONSTITUTION: Propylene oxide is isomerized at ≥200°C, preferably 200-350°C using lithium phosphate being ≤3% in content of the compound having ≤1μm particle size and having average particle size being in the range of 3-20μm and containing the compound having 1-10μm particle size at an amount of ≥70% as a catalyst while suspending the catalyst in an organic solvent (e.g., alkylbenzene or arylbenzene) having ≥200°C boiling point to provide the aimed compound. Contact time of propylene oxide with the suspension of the catalyst is preferably in the range of 3-20sec. Furthermore, the catalyst is used at a concentration of 3-10%, preferably 10-25%.