A sliding window system having an annular roller device for sliding windows and a door guide frame supporting the same, the sliding window system comprises, a chassis support unit formed integrally including a chassis seating portion formed at an upper center portion to accommodate a lower portion of the door chassis constituting the sliding window and a load support plate provided under the chassis seating portion; an annular rolling unit comprising a plurality of rolling members formed in a cylindrical shape provided in the transverse direction perpendicular to the door moving direction, and a chain link unit connecting two rolling members to each other so that the plurality of rolling members are evenly arranged in an annular shape on the surface of the load support plate at a set interval along the door moving direction, wherein annular rolling unit being wound around an upper surface and a lower surface of the load support plate of the chassis support unit and an arc of both ends formed on the side of the door traveling direction to connect the upper surface and the lower surface; and a door guide frame provided with a rolling support member along the door traveling direction to provide a rolling path of the plurality of rolling members constituting the annular rolling unit of the annular roller device for sliding windows, and further comprises, a straight guide unit which is provided for each of the plurality of rolling members constituting the annular rolling unit in order to roll along the travel direction of the door chassis without sliding left/right on the load support plate, wherein, the straight guide unit comprising, a first guide rail formed on the load support plate and formed around the load support plate along a traveling direction of the door chassis; a guide groove formed on an outer circumferential surface of each of the plurality of rolling members along a traveling direction of the door chassis to correspond to the first guide rail of the load support plate; and a second guide rail formed along the traveling direction of the door chassis on the upper surface of the rolling support body of the door guide frame to correspond to the guide grooves formed on the outer circumferential surfaces of each of the plurality of rolling members, wherein, the depth of the guide groove formed on the outer circumferential surface of each of the plurality of rolling members is set to be greater than the height of the first guide rail and the second guide rail, the sliding window system with an annular roller device being characterized in that the load support plate of the chassis support part is composed of two split bodies and along the sliding direction of the door (rail), and the connecting ends of two split bodies overlapping in the transverse direction are through-connected with a rotation pin. the sliding window system comprises, a chassis support unit formed integrally including a chassis seating portion formed at an upper center portion to accommodate a lower portion of the door chassis constituting the sliding window and a load support plate provided under the chassis seating portion; an annular rolling unit comprising a plurality of rolling members formed in a cylindrical shape provided in the transverse direction perpendicular to the door moving direction, and a chain link unit connecting two rolling members to each other so that the plurality of rolling members are evenly arranged in an annular shape on the surface of the load support plate at a set interval along the door moving direction, wherein annular rolling unit being wound around an upper surface and a lower surface of the load support plate of the chassis support unit and an arc of both ends formed on the side of the door traveling direction to connect the upper surface and the lower surface; and a door guide frame provided with a rolling support member along the door traveling direction to provide a rolling path of the plurality of rolling members constituting the annular rolling unit of the annular roller device for sliding windows, and further comprises, a straight guide unit which is provided for each of the plurality of rolling members constituting the annular rolling unit in order to roll along the travel direction of the door chassis without sliding left/right on the load support plate, wherein, the straight guide unit comprising, a first guide rail formed on the load support plate and formed around the load support plate along a traveling direction of the door chassis; a guide groove formed on an outer circumferential surface of each of the plurality of rolling members along a traveling direction of the door chassis to correspond to the first guide rail of the load support plate; and a second guide rail formed along the traveling direction of the door chassis on the upper surface of the rolling support body of the door guide frame to correspond to the guide grooves formed on the outer circumferential surfaces of each of the plurality of rolling members, wherein, the depth of the guide groove formed on the outer circumferential surface of each of the plurality of rolling members is set to be greater than the height of the first guide rail and the second guide rail, the sliding window system with an annular roller device being characterized in that the load support plate of the chassis support part is composed of two split bodies and along the sliding direction of the door (rail), and the connecting ends of two split bodies overlapping in the transverse direction are through-connected with a rotation pin.