The invention discloses a horizontal conveying device of composite cores. The horizontal conveying device of the composite cores comprises a support, a positioning mechanism, a steering mechanism, a tensioning mechanism and a conveying mechanism, wherein the positioning mechanism, the steering mechanism, the tensioning mechanism and the conveying mechanism are all arranged on the support; the positioning mechanism and the steering mechanism are sequentially arranged from bottom to top; the steering mechanism is located on one side of the tensioning mechanism; the conveying mechanism is located on the other side of the tensioning mechanism; a storage cavity for containing the composite cores is arranged below the positioning mechanism and defined by the support; and the composite cores are conveyed through the positioning mechanism, the steering mechanism, the tensioning mechanism and the conveying mechanism, and the conveying mechanism can conduct horizontal conveying on the composite cores. According to the horizontal conveying device, the stacked composite cores are conveyed upwards firstly and then horizontally, friction force caused when an existing device is used for conducting horizontal conveying on the composite cores directly is effectively reduced, the tensioning mechanism can arrange and flatten the composite cores, and the conveying quality of the composite cores is ensured.