A steam oven for an aircraft with a water leakage prevention function for cooking ingredients provided on an aircraft, comprising: two solenoid valves (6, 7) arranged in series on a water-supply line of the oven for controlling water supply; a controller for controlling a device of the oven and for sending a releasing signal or a closing signal to each of the solenoid valves (6, 7); and a solenoid valve power supply for supplying power to the solenoid valves (6,7), wherein the controller continuously sends a releasing signal to one of the solenoid valves (6,7), and at the same time, sends periodically repeating closing signals and releasing signals to the other solenoid valve (6,7), for a water supply, characterized by a water leakage prevention circuit including a clock pulse generator for outputting clock pulses with a predetermined frequency; an integrating counter for counting the number of pulses of the clock pulse generator; and an OR gate which receives the solenoid valve drive signals from the controller and the output of which is supplied to the clock pulse generator when the controller sends drive signals to the two solenoid valves (6,7), is provided in order to prevent water leakage beyond a dangerous level from occurring due to fail of the controller in control of the solenoid valves (6, 7) and the integrating counter counts the number of clock pulses while the OR gate outputs the specified signal, and the water leakage prevention circuit disconnects the solenoid valve power supply or a main power supply of the steam oven when a value counted by the integrating counter becomes larger than a count value corresponding to a predetermined water leakage amount, thereby forcibly putting the solenoid valve (6, 7) into a closed state. two solenoid valves (6, 7) arranged in series on a water-supply line of the oven for controlling water supply; a controller for controlling a device of the oven and for sending a releasing signal or a closing signal to each of the solenoid valves (6, 7); and a solenoid valve power supply for supplying power to the solenoid valves (6,7), wherein the controller continuously sends a releasing signal to one of the solenoid valves (6,7), and at the same time, sends periodically repeating closing signals and releasing signals to the other solenoid valve (6,7), for a water supply, characterized by a water leakage prevention circuit including a clock pulse generator for outputting clock pulses with a predetermined frequency; an integrating counter for counting the number of pulses of the clock pulse generator; and an OR gate which receives the solenoid valve drive signals from the controller and the output of which is supplied to the clock pulse generator when the controller sends drive signals to the two solenoid valves (6,7), is provided in order to prevent water leakage beyond a dangerous level from occurring due to fail of the controller in control of the solenoid valves (6, 7) and the integrating counter counts the number of clock pulses while the OR gate outputs the specified signal, and the water leakage prevention circuit disconnects the solenoid valve power supply or a main power supply of the steam oven when a value counted by the integrating counter becomes larger than a count value corresponding to a predetermined water leakage amount, thereby forcibly putting the solenoid valve (6, 7) into a closed state.