As is known well, the inflationary universe model resolves most of the fundamental problems concerning the large scale structure of the universe and is now becoming a standard model for the early universe. However, there is one important problem yet to be made clear. In this model the number density of particles effectively goes to zero during the inflation and everything is created after the universe is heated up again at the end of inflation. Since the reheating temperature is much lower than the GUT temperature in general, however, it is not clear whether the observed baryon asymmetry is generated in this process.