To provide a forming method of a composite coating film, by which a crosslinked coating film as a lower layer which can be removed with a specified compsn. is formed and then a substantial coating film is formed on the lower layer, and to provide a method to remove the whole coating films by removing the lower coating film.

This composite coating film is formed in the following process. First, a coating material containing a binder of a resin having a chemical structure expressed by the formula is applied on the object body to form a lower coating film (A). Then, a coating material which is used for coating substantially is applied to form an upper coating film (B). The formed coating films are removed by bringing into contact with a mixture (C) containing (i) an acid compd. and (ii) water as the essential components.