Refers specifically to a person who conducts an interview, typically in a formal setting like a job interview or entrance examination.
The interviewer asked detailed questions about my background.
面接官 is a more common and slightly less formal synonym for 'interviewer'. 面接試験官 explicitly includes the nuance of a formal examination setting.
Compound of 面接 (interview) + 試験 (examination) + 官 (official). The term is transparently derived from its components.