A sulfurization detection sensor 10 comprises: a rectangular parallelepiped insulation substrate 1, a pair of front electrodes 2 provided at both ends of a front surface in the longitudinal direction of the insulation substrate 1, respectively, a sulfurization detection conductor 3 connected between the front electrodes 2, a pair of protective films 4 for covering a part of the sulfurization detection conductor 3 and that of the front electrodes 2, respectively, a pair of back electrodes 5 provided at both ends of a back surface in the longitudinal direction of the insulation substrate 1, respectively, a pair of end face electrodes 6 provided at both ends in the longitudinal direction of the insulation substrate 1, respectively, and external electrodes 7 provided on front surfaces of the end face electrodes 6, respectively. Specific regions 3b in which a current hardly flows are formed at both ends in the Y-direction of a sulfurization detection portion 3A.