A linear solenoid is configured with an electromagnetic coil and a label resistor that are integrated with each other; the label resistor has a resistance value corresponding to a correction coefficient based on the difference between the actual characteristic of the supply current vs. adjusted hydraulic pressure output of the electromagnetic coil and a standard characteristic; and data for correcting a characteristic variation in the command current vs. output current characteristic of an electromagnetic coil is preliminarily stored in a control module by use of an adjustment tool. When the operation is started, the resistance value of the label resistor is read and an output current corresponding to a utilized linear solenoid is supplied, so that a target adjusted hydraulic pressure is obtained.