Corrosion of silicon nitride was studied in boiling nitric acid to examine its feasibility as a drying pan material in the reprocessing of nuclear fuel. Unlike stainless steel (a conventional drying pan material), the weight loss and strength degradation were negligible in the concentration of nitric acid. The corrosion increased with decreasing concentration of nitric acid. At the concentration of 1-6N, the maximum losses of weight and strength were 0.8% and over 40%, respectively, in 200 h. Ionic species dissolved in nitric acid were determined by ICP analysis and were found to be accurately correlated to the weight loss and thickness of the corrosion layer determined by micrography. In the corrosion layer, grain boundary glassy phase was selectively dissolved. Strength loss was correlated to the weight loss and was ascribed to the reduced load bearing area due to corrosion.