To suppress gas escape and to enable long-term display by inserting a balloon-like inner skin of a separate body made of a plastic film provided with a gas barrier layer on its outer layer into a balloon-like outer skin made of a transparent plastic film provided with a gas barrier layer on its intermediate layer.

The outer skin 2 of the balloon body which is constituted by housing the inner skin 3 which is the separate body in the outer skin 2 as the composite plastic film balloon, is formed of the transparent plastic films 4 of a three-layer structure laminated, successively from the inner side, with a polyethylene (PE) layer 4a, the gas barrier layer 4b using an ethylene-vinyl alcohol copolymer and a PE layer 4c. On the other hand, the inner skin 3 is formed of the plastic films 7 of the three-layer structure having an excellent gas barrier property and elongation. The films 7 are formed by providing the films with the straight chain low-density polyethylene layer 7a, the nylon layer 7b and the gas barrier layer 7c vacuum deposited by evaporation on its front surface successively from the inner side and a printing surface 7d is formed thereon at need.