The office of the chief, would be a place you go to see the person in charge, if we are speaking in a professional term, this person would be your boss or the CEO of that company, as for the other phrase I, being a English teacher haven't heard of it being used in normal conversation. Any other questions you have feel free to contact me.

Most top positions at big companies begin with the word "chief": CEO – Chief Executive Officer (head of the company) CAO – Chief Administrative Officer (responsible for internal affairs, e.g. human resources etc.) CFO – Chief Financial Officer (in charge of financial issues) CIO – Chief Information Officer (responsible for information about the company most of the times also responsible for the IT-section) https://englishinbusiness.wordpress.com/2007/11/29/ceo-coo-cfo/