Little is known about the soil faunal community involved in the decomposition of fine-root litter, although the quantitative importance of fine roots has been frequently mentioned. The collembolan communities involved in root and leaf decomposition were compared in a two-factor litter bag experiment (litter type x litter position), and the relative effects of litter quality and litter position were evaluated. Litterbags of roots and leaves were each placed at two positions (on the soil surface and in the soil), and collected over three years. Collembolan abundance and community composition largely differed between root and leaf litter decomposition at each natural position. The differences between root and leaf decomposition were mainly caused by litter position, but effects of litter type were also detected on species-level community composition. Species that preferred roots were abundant in the early stage of litter decomposition in the soil. Because the early stage of decomposition in the soil is naturally achieved only by root litter initially deposited in the soil, root litter may function as an essential resource for certain species. The results of this study indicate that root litter contributes to collembolan community organization as a spatially and qualitatively different resource than leaf litter.