Various test methods have previously been adopted to test large deployable space structures. However, traditional methods are not applicable to a precise evaluation of three-dimensional deployment characteristics with quasistatic deployment motions. This paper describes the design and performance of a deployment test system using magnetically suspended sliders. The sliders support the deployable structure vertically, and each of them moves freely with negligible friction under the horizontal surface of a ceiling plate. All the sliders control the tension of their vertical cables independently using the feedback signals of the tension sensor to compensate for the gravity of the deployable structure. The test system using magnetically suspended sliders enables maximum drag with a horizontal motion of less than 0.25N and tension control precision from a suspension cable of within 0.25N. The adequacy of this test system is confirmed by a deployment test using a 7m test model.