Abstract: In a flow quantity control valve of the type comprising a rod shaped valve moved toward and away from an orifice formed in a fluid passage for controlling flow quantity of an operating fluid supplied to a power steering device of a motor car, for example, and drive means for reciprocating the rod shaped valve with respect to the orifice, there is provided an annular permanent magnet loosely encircling the rod shaped valve and located close to the orifice for attracting and removing magnetic particles contained in the operating fluid where the drive means is constituted by a solenoid coil and a plunger, current supplied to the solenoid coil is adjusted in proportion to a running speed of a motor car.