To provide a method for the production of propylene oxide which effectively performs an epoxidation reaction, controls the loss of an active substance and reduces the energy required in the purification of propylene oxide, in a method for producing propylene oxide which comprises a process (epoxidation process) of reacting an organic peroxide with propylene in the presence of a catalyst, to prepare propylene oxide and alcohol, a process (propylene recovering process) of recovering the unreacted propylene in the epoxidation process and recycling the propylene to the epoxidation process as a raw material for the process, and a process (purification process for propylene oxide) of purifying the propylene oxide by subjecting the propylene oxide produced in the epoxidation process to a distillation process.

The concentration of the organic peroxides in the liquid reaction mixture after the epoxidation process is controlled at 20-5,000 wt.ppm (based on the amount excluding the propylene present in a liquid reaction mixture).