(Abstract) This paper designs the rotor structure for two types of permanent magnet synchronous motors. The proposed optimization method combines a topology optimization method, which uses a genetic algorithm and a cleaning procedure, and a method considering ease of manufacturing. The designed rotor of a compressor motor for an air conditioner has 32 % higher average torque than that of a conventional motor. The designed rotor has a larger torque/current than that of a hybrid vehicle motor at a low output power.