There is provided an apparatus for measuring a position of a linear type valve which is open/shut by operation of a hydraulic cylinder. More particularly, the apparatus more accurately measures a valve position by outputting a rotation angle of a rotation sleeve which rotates by being operatively connected to a hydraulic cylinder which moves linearly, and by calculating a vertical movement distance of a valve gate which changes in proportion to the rotation angle. Further, since the structure of the apparatus is very simple, the cost of production is significantly reduced. In addition, for use, the apparatus is installed on the hydraulic cylinder by a simple method.