"It's a great privilege to have then come. Our city's been a magnet for big companies," Spitaleri said, pointing out that Apple, Google, Nokia, Hewlett Packard and others already have offices in Sunnyvale.
"Companies want to go where they see a stable community, and we represent that," he said.
An unveiling and tour of the new 237,121-square-foot office space at 1020 Enterprise Way was scheduled for midday Monday.
Based in Washington state, Microsoft also has California offices in Mountain View, San Francisco and Sacramento, and employs more than 2,500 people in the Bay Area.
"The opening of the Moffett Towers office represents our commitment to Microsoft Silicon Valley as a strategic location for the company in the heart of a rich technology ecosystem and talent pool," Qi Lu, president of Microsoft's Online Services Division, said in a statement.