A process for producing propylene oxide, which comprises the following steps: oxidation step: a step of obtaining cumene hydroperoxide by oxidizing cumene; epoxidation step: a step of obtaining propylene oxide and cumyl alcohol by reacting cumene hydroperoxide obtained in the oxidation step with propylene; and conversion step: a step of obtaining cumene by subjecting cumyl alcohol obtained in the epoxidation step to hydrogenation-containing reaction and recycling the cumene to the oxidation step, wherein a concentration of 1,2-epoxy-2-phenylpropane contained in the reaction mixture after the oxidation step, is 1% by weight or less.