A process for producing propylene oxide, which comprises steps described below, wherein the concentration of ethylbenzene in a solution containing isopropylbenzene to be recycled to the oxidation step is 10% by weight or less: oxidation step; a step in which isopropylbenzene is oxidized to obtain isopropylbenzene hydroperoxide, epoxidation step; a step in which isopropyl hydroperoxide obtained in the oxidation step is reacted with propylene to obtain propylene oxide and cumyl alcohol, and hydrogenolysis step; a step in which cumyl alcohol obtained in the epoxidation step is subjected to hydrogenolysis to obtain isopropylbenzene, and said isopropylbenzene is recycled to the oxidation step as a raw material for the oxidation step.