A battery diagnosis device includes: one or more sensors which measure at least one of a current value, a voltage value, and a temperature value of a battery; a first determination unit which acquires, from the sensor, at least one of measured values of the current value, the voltage value, and the temperature value of the battery, and determines a state of the battery by using a first method, based on the acquired measured values; a second determination unit which acquires, from the sensor, at least one of measured values of the current value, the voltage value, and the temperature value of the battery, and determines the state of the battery by using a second method different from the first method, based on the acquired measured values; and a diagnosis unit which diagnoses the battery, based on determination results of the first determination unit and the second determination unit.