A stroke sensor system includes a conductor, a coil which moves relative to the conductor and is fitted to one end side of the conductor; and a ferromagnetic body which is arranged on an end position side of the coil. A position of an end portion on one end side of the conductor in a state where a fitting ratio between the conductor and the coil is maximized is defined as the end position. The ferromagnetic body is located on an opposite side to the conductor with the coil interposed therebetween.