PURPOSE: To simply prevent oil leak by providing a hollow guide member extending through a coupling part of a moving coil and a spool and fixed to a holder, leading a displacement sensor output line through the guide member to the inside of a valve body and taking out the output line together with moving coil exciting wiring through a connector of the valve body.

CONSTITUTION: A bobbin 14 of a coupling part of a moving coil 11 and spool 10 at one of the spool 10 is coupled with a core 24 of a position detecting rod, and a permanent magnet 17 is disposed on the outer periphery of the moving coil 11 and a coil 25 of a displacement sensor on the outer periphery of the core 24. A holder 13 is provided inside the valve body 12 with a projecting guide 30 and the bobbin 14 is formed with a hole 14A through which the guide 30 extends displaceably axially. The output line 23 of the coil 25 is led through hollow part of the guide 30 into the valve body 12 to be connected through a connector 16 of the valve body 12 to a servo amplifier 15 together with exciting wiring 19 of the moving coil 11. Thus, only one connector makes oil leak from the holder difficult.