A risk-degree setting unit (108) sets the degree of risk for the case where an inverter (103) performs conversion processing (inverter risk degree), and sets the degree of risk for the case where a storage battery (105) stores electrical energy (storage battery risk degree). A final output destination determination unit (109), based on the degrees of risk set by the risk-degree setting unit (108), determines the final output destination of electrical energy output from an electric motor (106), and controls the turning ON or OFF of a relay (110). The final output destination determination unit (109) turns the relay (110) ON when the storage battery (105) is determined as the final output destination of the electrical energy output from the electric motor (106), and turns the relay (110) OFF when the inverter (103) is determined as the final output destination of the electrical energy output from the electric motor (106).