Abstract: A terminal fixing structure which includes a cylindrical ceramic base with a conductive contact on the side and a metal thermal with a pair of resilient arms for holding the side of the ceramic base and for contacting the conductive contact. The ceramic base has an engaging receptor on the side and each of the arms has an engaging portion for engaging with the receptor. Since the engaging receptor (e.g., ring grooves) of the ceramic base is firmly engaged with the engaging portion (e.g., teeth), the ceramic base and the terminal will not be separated from each other by a vibration, etc. An oxygen sensor using this terminal fixing structure is one possible application.