The present study is aimed to evaluate forest health in a fragmented urban forest using insects which are rarely used for evaluation of forest health. It is supposed that forest would be health if insect community in an urban forest is similar to that in healthy forests. Ants (Formicidae) and ground beetles (Carabidae) surveyed by pitfall trap method in the Hongneung forest located in the urban area of Seoul were compared with those in the Gwangneung forest. The Gwangneung forest is supposed to be health due to its high biodiversity and well-conserved nature. Ants of the Hongneung forest was much more abundant compared with those of the Gwangneung forest. However, ground beetles showed the opposite patterns; much more abundant in the Gwangneung forest than in the Hongneung forest. Species richness was higher in the Gwangneung forest than in the Hongneung forest, but species diversity was higher in the Hongneung forest. This dominance decreased species diversity in the Gwangneung forest. Thus, characteristics of insect community in the Hongneung forest were greatly different with that in the Gwangneung forest. This great difference of insect communities between the target and reference sites may indicate whether the Hongneung forest would not be health according to the working hypothesis, or may indicate simply the characteristic of the fragmented urban forest. In order to determine the significant decision, the repetitive studies are needed on this regard.