The present invention relates to a diagnostic device of a transformer. According to an embodiment of the present invention, the diagnostic device of a transformer includes: a partial discharge sensor detecting ultrasonic waves generated by partial discharge to generate a partial discharge signal when partial discharge occurs inside the transformer; a vibration measurement sensor generating a vibration signal by detecting the vibration generated from the transformer when the transformer is activated; and a diagnosis unit for diagnosing the state of the transformer using the partial discharge signal and the vibration signal. [Reference numerals] (1) Transformer; (30) Diagnosis unit
