Quantitative analysis of thermal degradation of poly(phenylene ether) (PPE) has been attempted by a computer simulation model named ''Molic mouse model''. The model was designed to simulate individual steps, each corresponding to an organic reaction in the thermal degradation. The rearrangement reaction of the main chain, the cleavage reactions of ether and methylene bridge between benzene rings, and the elimination of a methyl group from a side chain were selected. Each reaction was assumed to occur if a generated random number was greater than its probability, which had been determined by fitting the distribution of monomeric scission products in prior simulation. The result was verified by predicting the distribution of dimeric scission products. The individual reaction rates during PPE thermal degradation could be estimated by the Molic mouse model for the first time.