A total of 96 species and four indeterminable species in 35 families of polychaetous annelids are reported from 68 otter trawl samples collected from Tosa Bay. Seven species or subspecis are new to science: Aphrodita macroculata and Aphrodita tosaensis (Aphroditidae), Phyllodoce lineata tosaensis (Phyllodocidae), Euphrosine tosaensis (Euphrosinidae), Eranno tosaensis (Lumbrineridae), Asychis tosaensis (Maldanidae) and Melinnexis tetradentata (Ampharetidae). Five species are new to the Japanese polychaetous fauna: Pholoides dorsipapillatus {Pholoidae), Leanira caeca (Sigalionidae), Phyllodoce groenlandica (Phyllodocidae), Onuphis eremita parva (Onuphidae) and Travisia kerguelensis intermedia (Opheliidae}. The best-represented families are: Onuphidae (16 species), Maldanidae (11 species), Syllidae (9 species), Aphroditidae, Eunicidae and Serpulidae (5 species each). A description is presented.