To provide a flow control valve in which a worm wheel can be corrected in phase without allowing the worm wheel to abut against a stopper.

There is provided a flow control valve in which the worm wheel 6 is allowed to engage with a worm gear 51 rotating by means of a stepping motor 5 to be rotated and then the rotating movement of the worm wheel 6 is converted into a linear movement to reciprocate a valve body 2. In the flow control valve, the worm wheel 6 is held in freely rotatable manner so as not to move in a rotational-axis direction of the worm wheel 6 and besides a permanent magnet 7 is fitted on a lateral side of the worm wheel 6. A magnetism detector 71 is fixed to a position opposed to the permanent magnet 7, thus enabling a rotational phase of the worm wheel 6 to be detected.

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