Structure of supercritical fluid and its component clusters has been investigated by large-scale and long-time (N = 10,976, t = 1 ns) molecular dynamics calculations along an isotherm at T = 1.03 T-c at various densities ranging from gas-like region to liquid-like one. Intra-cluster radial distribution function, distribution of angle formed by three molecules in the cluster, and asphericity parameter distribution function indicated bulky and fractal-like structure of the clusters. Clusters of the same size in the fluid at different densities showed almost the same structure independent of the fluid density.