The present invention is to provide an inflatable bag comprising an airtight container, a cavity and a light-emitting unit. The cavity is formed at a top of the container. The cavity comprises a top opening flush with the top of the container, the opening being in communication with the container and the external. The light-emitting unit is mounted in the cavity by inserting through the opening. The light-emitting unit comprises a battery, a light-emitting member provided at a bottom in the cavity distal the opening, and a switch provided at a top projecting from the cavity. The battery is not electrically connected to the light-emitting member after inflating the container to a predetermined shape. The bag is adapted to emit light only by pressing the switch projected from the container to electrically connect the battery to the light-emitting member.