Provided is a battery pack with improved heat dissipation efficiency. The battery pack includes a holder case, and a plurality of batteries disposed inside the holder case. The holder case includes a plurality of ribs disposed inside the holder case. Each of the ribs has a column extending in a direction substantially parallel to a side surface of the holder case, and each of the batteries is accommodated between the columns of the ribs. The column has a heat dissipation hole therein extending along the extension direction of the column. An air flow is formed through the heat dissipation hole, and heat generated during a charge and/or discharge operation dissipates through the air flow in the heat dissipation hole. A portion of the columns are separated from each other forming a gap. The heat generated from the batteries also dissipates through this gap.