An electric coupler for a lighted inflatable device comprising a base attached to a cloth of a lighted inflatable device at the inside through the process of heat sealing with a passage way defined therein for inserting a light string from the outside into the lighted inflatable device, and a sealing cap to block up the passage way is disclosed. The sealing cap has terminals for connecting an external power supply to the light string inserted inside the lighted inflatable device by connectors. The light string is separately packed during delivry, and inserted inside the lighted inflatable device when in use.