Abstract: To clarify the effects of artificial acid rain on soil macroinvertebrates, a field study was done in an oak and a japanese cedar stands in Tanashi experiment station, The University of Tokyo from 1996 to 1998. 135 ceramic pots filled with black soil relatively free of soil macroinvertebrates were taken and sunk into the ground of each study sites. The pots were perfused by 400 mL tap water or acidic water (0.015 and 0.030% solution) once a week from April to October. Soil macrofauna were collected from the pots after one- year or two-year treatment. The results showed that acidic water generally decreased the density and biomass of soil macroinvertebrates. The clearest negative effects of acidic water were found on taxa Trachelipidae (Isopoda) and to some extent on Oligochaeta and larvae of Diptera.