An electronic device is provided, which may include a first housing; a second housing configured to accommodate at least a portion of the first housing and guide a sliding movement of the first housing; a display including a first display area disposed on the first housing and a second display area extending from the first display area; a PCB configured to accommodate at least one electronic component; a support member configured to support the PCB; a side wall member connected to the support member and facing at least a portion of the first housing; a heat dissipation sheet configured to receive heat from the at least one electronic component, the heat dissipation sheet being disposed on the support member and the side wall member; and a heat dissipation member disposed on the side wall member and facing the heat dissipation sheet.