A novel software "AVS/Express PCE", which runs on commodity-based PC cluster, was developed to visualize a large-scale data set efficiently. This system allows users to customize functions without any parallel knowledge and provides parallelized processes for almost all of processes such as I/O, filtering, mapping, and rendering. It is very effective to parallelize all processes but the image compositing becomes a bottleneck for a parallel rendering system. To avoid this problem, a special hardware that can synthesize an output image from input images without significant delay was combined to the software. According to preliminary test results, the present system performed about 4 frames per second to update iso-surfaces for a million grids field data.