DIAGNOSTIC DEVICE AND SENSOR

Provided are a low cost diagnostic device and a sensor capable of detecting functional failure and deterioration of a PM sensor early. There is provided the diagnostic device for a sensor 10 which is arranged in an exhaust passage 110 of an internal combustion engine 100 and detects a particulate matter amount in exhaust, the diagnostic device including a time-rate-of-change calculation unit 2 which calculates a time rate of change of the particulate matter amount detected by the sensor 10 during a period in which a fuel injection amount of the internal combustion engine 100 is equal to or less than a predetermined injection amount threshold, and an abnormality determination unit 3 which determines an abnormality of the sensor 10 based on the time rate of change of the particulate matter amount calculated by the time-rate-of-change calculation unit 2.