There are many research results on creep and relaxation aiming at investigating the time-dependent behavior of rock. However, rock mass around gateways in mines or underground structures deforms accompanied with both stress and strain change. Fukui et al. (1992) proposed the generalized relaxation test where both stress and strain change keeping the ratio between them constant. In this study, computer simulation was carried out to explain their results. The non-liner Maxwell model was used in the simulation and the calculated results well coincided with the experimental results except those in high stress level in which strain/stress rate were considerably larger than the calculated results.