An electromagnetic actuator, which is arranged at a position opposing to a hydraulic control valve, has a movable-core chamber for movably accommodating a movable core and an air breathing passage for communicating the movable-core chamber to the atmosphere. An inside opening of the air breathing passage is formed in an inner wall of the movable-core chamber, while an outside opening of the air breathing passage is formed in an outer wall of the actuator, which is in contact with the atmosphere. The outside opening is formed at such a position out of an oil-splashing area, to which oil discharged from an oil-discharge port of the hydraulic control valve is directly splashed. According to the above structure, it is possible to prevent the oil discharged from the oil-discharge port from rushing into the movable-core chamber through the air breathing passage.