An apparatus and method suitable for producing a polymer film, particularly a polyimide film, perform drying and heat treatment using a tenter type feeding apparatus that suppresses the problems of deformation of film in the vicinity of pore into which the pins bite and breakage of the pores to form long pores in the width direction. The apparatus includes a device to suppress deformation of the film in the vicinity of the tenter pins at the time point when the both ends of the film is pierced with the pins and cools the pin temperature to less than 180° C. at the time when the film is pierced with the pins. Individual pins can be arranged on the innermost side of the pin sheets so that they are all disposed at the same distance both in the film feeding direction in the individual pin sheets and between other pin sheets.