personnel department vs personnel office

personnel department and personnel office both are nouns.

Word	Noun	Adjective	Verb	Adverb
personnel department	Yes	No	No	No
personnel office	Yes	No	No	No

As nouns, personnel department and personnel office are synonyms defined as:

personnel department and personnel office: the department responsible for hiring and training and placing employees and for setting policies for personnel management

Other synonyms of personnel department include personnel, staff office.

personnel department (noun)	personnel office (noun)
the department responsible for hiring and training and placing employees and for setting policies for personnel management	the department responsible for hiring and training and placing employees and for setting policies for personnel management