Provided is a battery pack processing apparatus and a processing method with which discharge can be performed in a short time when a battery pack is discharged by immersing the battery pack in a discharge liquid.A processing apparatus A is for discharging a battery pack P having single cells c and a case b by immersing the battery pack P in the discharge liquid. The processing apparatus A includes an aperture-forming machine 20 forming an aperture through which the discharge liquid can flow inside the case b by pressurizing the battery pack P. A state can thus be achieved which is the same as the state that results if the single cells c accommodated in the case b are individually immersed in the discharge liquid. A protection circuit f for preventing an over-discharge is prevented from suppressing a discharge current from the battery pack P, enabling the discharge in a short time.