In a solenoid of a hydraulic pressure control apparatus, a region adjacent to an oil flow guide portion of a stopper breathing passage is formed in a magnetism application region, through which a leakage magnetic flux leaking from a magnetic circuit at a time of turning on of a coil passes. Thereby, magnetic foreign objects made of iron or iron containing material are magnetically attracted to the leakage magnetic flux, so that intrusion of the foreign objects from an outside of the solenoid into a second volume variable chamber through the stopper breathing passage is limited.