An abnormality determination apparatus, which determines abnormality of a temperature sensor in a machine tool, includes: a temperature pattern storage unit which stores a normal pattern indicating temperature change relative to machining time for a machining classification of the machine tool; a temperature data acquisition unit which acquires temperature data outputted by the temperature sensor provided to the machine tool; a machining classification determination unit which determines a machining classification of the machine tool; a comparison data acquisition unit which extracts the normal pattern relative to a determined machining classification from the temperature pattern storage unit; a comparison unit which compares the extracted normal pattern, and as acquired pattern indicating temperature change relative to machining time according to the acquired temperature data; and an abnormality determination unit which determines abnormality of a temperature sensor based on a comparison result.