The effects of forest management using simple cable yarding and group cutting effects on suspended soil outflow and runoff characteristics were examined with paired watershed method. A maintained watershed (6.65 ha) and a control watershed (8.53 ha) were set in the Kaisawa experimental basin in Kanagawa prefecture. The vegetation is an artificial plantation of Japanese cedar and cypress. Part of the watershed comprises Japanese oak. Forest management was conducted by combining group cuttings in a small area (20 m×20 m) in five places. Then selective logging was practiced throughout the maintained watershed. The thinning rate became 17 %. Management was conducted without using heavy industrial machinery inside the experimental site and using a simple cable yarding system. The stream system was left undisturbed. No new forest road was constructed. After forest management, increase runoff from the maintained watershed was observed. The increased runoff quantity was 100 mm at the annual rainfall amount (1,800 mm). Derivation of the increased runoff quantity was estimated as 60 mm from the base flow component and as 40 mm from the direct runoff. No increased suspended sediment flow quantity was recognized after forest management. These results demonstrate that forest management by a simple cable yarding system conducted at this experimental site was adequate to maintain less sediment production in the watershed.