To evaluate the stabilizing effects of tree diversity on each feeding type of herbivore insects simulated increasing N situation, we performed a large-scale N fertilization (100kg N ha-1 y-1) experiment for 4 years in a deciduous broad-leaved forest of Tomakomai Experimental Forest (TOEF), Hokkaido in northern Japan. We assessed the stability of each feeding type of herbivore insects on an oak species (Quercus crispula) across tree diversity gradients between control (ca. 10ha) and fertilized (ca. 9ha) sites. We found that tree diversity did not affect the stability of chewing and leaf-mine insect' communities both sites, but deciduous trees/ conifer trees ratio and oak dominancy increased the stability of galler's community in only control site. Our results suggest that the mechanism driving the diversity-stability relationships might have species - specific response, and N deposition might disturb a positive relationship between stability of galler's community and the forest composition.