The present invention provides a production method and an apparatus for double curve formed products for producing double curve formed products easily at low cost, stabilizing an accuracy in configurational dimension of the double curve formed product and improving an accuracy in assembly thereof, the production apparatus being of a simple construction apparatus. Around an inner die in which an end portion of a treatment product is engaged, an outer die in which the other end portion of the treatment product is engaged is rotated relative to each other at predetermined angles. At this time, a side face of the treatment product is curved so that it is successively folded back. By a deformation reaction caused at this time, the side face of this curved portion is pressed against a processing curved surface of the inner die such that the side face is deformed along the processing curved surface. Another side face of the treatment product is pressed against a processing curved surface of the outer die such that it is deformed along the processing curved surface. As a result, in the treatment product, one curved surface is formed along the processing curved surface of the outer die and the other curved surface which is continuous from the one curved surface which is folded back is formed along the processing curved surface of the inner die.