1. A large-scale graph processing system using GPUs, comprising: a main memory including graph data; device memories of a plurality of GPUs that process the graph data transferred from the main memory; a loop controller that processes 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 streaming controller that copies the graph data to the device memory of the GPU in a chunk or streaming manner using a GPU stream according to the nested loop join scheme.