Many paddy fields in the mountainous rural areas of Japan have been abandoned since the 1960s, and forests have regenerated on these sites. In a mountainous area on Sado Island, a large number of abandoned paddies were converted into wetlands and open terrestrial vegetation. In this study, we used pitfall traps to examine the effects of the creation of open vegetation on carabid beetle assemblages by investigating 14 sites spanning five vegetation types: six sites in secondary forests (three coppice forests and three 40-year-old regenerating forests on abandoned paddies), three each in clear-cuts and paddy levees, and two in grasslands. The 14 study sites were clearly separated into two groups different in the species composition of carabid beetles: secondary forest and grassland-levee groups. The species composition of two clear-cut sites was similar to that of secondary forests, whereas that of the remaining one clear-cut site was similar to that of grasslands. Analyses of species responses showed various habitat preferences, e.g., for only coppice forests, for two types of secondary forests, for secondary forests and clear-cuts, for clear-cuts and grasslands, and for grasslands or levees, or no clear preference. There were no characteristic species in the regenerating forests. These results suggest that the 40-year-old regenerating forests may sustain only a limited subset of the carabid fauna found in coppice forests and that the creation of open vegetation in the abandoned paddies enhances carabid diversity at the landscape level by raising β diversity among the different vegetation types.