A portable terminal device includes a connector that opens from a lateral surface of a case and electrically connects with another terminal device, an elastic connector cap that opens and closes an opening of the case, and a holder that maintains the opening in a closed state. The connector cap includes a first wall that protrudes perpendicularly to the lateral surface from a periphery of the opening located on one end of the case, and a second wall that protrudes from the other end of the case, is continuous with the first wall, and is coupled to swing freely to the other end. When the opening is closed, the first wall is exposed on a top surface of the case roughly perpendicularly to the thickness direction, and its distal end is located farther away from the opening relative to a coupling section of the second wall.