We examine the viscoelastic effect on earthquake cycle using a simple spring-dashpot-mass system with a laboratory-derived friction law. The temporal change of the frictional stress is large at the early interseismic stage and gradually decreases, in contrast to the linear change in an elastic medium. This temporal change depends on the Maxwell time. The smaller relaxation time leads to the larger change of the stress accumulation rate. Such a rate change in stress accumulation may affect the seismicity at subduction zones. Moreover, we find that the smaller relaxation time produces the smaller period of earthquake cycle and that, if the system relaxation time becomes smaller than the period of earthquake cycle, the bifurcation phenomenon, where the period splits into two, occurs. It is also found that the smaller relaxation time causes the earlier occurrence of the precursory stress decrease preceding the rapid stress drop. ¿ 2001 American Geophysical Union