A battery pack fixing apparatus which may effectively prevent a battery pack from being detached or separated from the fixing apparatus and may ensure easy installation regardless of the place where the battery pack is mounted, including a support unit supporting a lower portion of the battery pack and having a support plate with a coupling structure coupled to the lower portion of the battery pack; and a wall fixing unit including a fixing plate located at the rear of the battery pack loaded on the support unit, formed with a plate shape erecting upward, having a lower portion coupled to one side of the support unit and having a coupling structure coupled to a wall located at the rear.