Japanese spiders of the genus Dolomedes are revised and its phylogeny is inferred by mt-DNA. Dolomedes japonicus Bösenberg & Strand 1906 and D. angustivirgatus Kishida 1936 are removed from the synonymy. Dolomedes fimbriatoides Bösenberg & Strand 1906 and D. hinoi Kayashima 1952 are newly synonymized with D. sulfureus L. Koch 1878, and D. stellatus Kishida 1936 is synonimized with D. japonicus. Two new species, D. fontus and D. silvicola are described. Relative leg length and proportion of male palpal tibia are considered as good keys to indentify Dolomedes spiders, whose genital organs closely resemble one another. Dolomedes sulfureus and D. silvicola, often found on vegetation, have much longer legs and male palpal tibia than their relatives that inhabit near water and run on water surface or hide under water when disturbed. Molecular phylogenetic analysis using mt-COI revealed the following; ((((raptor, yawatai), japonica), orion), (((angustivirgatus, sulfureus), fontus), (silvicola, saganus)), horishanus).