The macro-benthos research was carried out in different seasons from 1997 to 1998 to clarify the characteristics of macro-benthic diversity in Honjo-Area of Lake Nakaumi, Shimane Prefecture. The number of macro-benthic individuals and the diversity, as well as the quality of bottom water and bottom sediment are reported here. Though the distribution of benthic animals pretends to be changeable due to the complex bottom condition caused by artificial change, Musculus senhousia, an epifaunal bivalve closely attached with byssus, is dominant as a whole in each period of investigations and its mat-like colony produces a preferable habitat for such polychaetes as Pseudopolydora kempi.