1. A large-scale graph processing system using GPUs, comprising: a main memory including graph data; device memories of a plurality of GPUs that are configured to process the graph data transferred from the main memory; a first processor configured to process graph data transfer in a nested loop join scheme in the graph data transfer between the main memory and the device memory of the GPU; and a second processor configured to copy the graph data to the device memory of the GPU in a chunk and/or streaming manner using a GPU stream according to the nested loop join scheme; wherein the second processor is configured to copy outer data included in the graph data to the device memory of the GPU in a chunk manner, and copy inner data included in the graph data to the device memory of the GPU in a streaming manner, and the large-scale graph processing system is configured to process the graph data by using the GPUs, a scale of the graph data being greater than a capacity of the device memory of the GPU.