This solenoid actuator 100 is configured so that a plunger 17 is axially moved by a magnetic force generated by electrically energizing a coil 11, and the drive section 3 of a device 110 to be driven is driven by the movement of the plunger 17. The solenoid actuator 100 is provided with a stator 12 which accommodates the plunger 17, a yoke 10 which accommodates the coil 11 disposed on the outer peripheral side of the stator 12, and a mounting section 20 which is connected to the stator 12 and which is mounted in a threaded hole 2d in the device 110 to be driven. The outer periphery of the mounting section 20 is disposed inside the outer periphery of the yoke 10.