The operation of the KEKB accelerator at KEK started on December 1998 after about 4 years' construction. More than 2000 vacuum chambers and their attachments were installed progressing through some stages in last 2 years. Each stage was set with specified procedure and under careful quality control. The average base pressure in the order of 10(-8) Pa just before the commissioning, and the following decrease of photon stimulated gas desorption proved the validity of our procedures.