Increase in the density of sika deer (Cervus Nippon) has had a significant impact on the forest ecosystem of Japan. Among many studies on the deer impact, few have examined the impact onto forest communities at early successional stages, where functional diversity of insects could be extremely high. In this study, we aimed to describe deer-induced changes of early-successional plant-and-insect communities at various trophic levels. The studies were conducted at secondary forests in southeast Boso Peninsula, where deer density had been high. We collected insects using FITs, and surveyed ground-layer vegetation inside and outside of deer exclosures. We also took same datasets at another site where deer had not existed for long. Plant biomass was significantly higher inside the exclosures than outside, though plant species richness was not significantly different between inside and outside of the exclosures. Species richness of insects outside the exclosures was higher than that inside exclosures. Strong correlation was found between species richness of parasitic wasps and that of all other insects. However only weak correlation was found between species richness of predacious insects and that of herbivore insects. From these results, insects of higher trophic levels are expected to be more strongly influenced by deer.