The present invention relates to a transformation relay and a battery voltage measurement system using the same. The transformation relay comprises: a transformation unit for transforming the voltage of a voltage measurement signal according to the turn ratio of a primary winding and a secondary winding; and a relay unit which, if the voltage of the transformed voltage measurement signal is inputted, is switched on to transmit the voltage of a battery. The battery voltage measurement system using the transformation relay comprises: the transformation relay; and a measurement unit for receiving the voltage of the battery from the relay unit and measuring a battery voltage value.