An inkjet printer comprising: a platen having a placing face on which a printing medium in an elongated sheet shape is held; a printing means which is provided with a printer head that is oppositely disposed to the placing face of the platen and that ejects ink to a printing target region of the printing medium to perform printing and in which ink is ejected while the printer head is relatively moved to the printing medium that is placed on the placing face of the platen to perform printing on the printing medium; a printing medium feeding means which feeds the printing medium that is placed on the placing face of the platen out from the platen depending on the printing by the printing means; a front platen which is provided on a feeding-out side where the printing medium is to be fed out with respect to the platen and which is provided with a guide face on which the printing medium having been fed out from the placing face of the platen is placed and held; a printing medium temperature raising means which heats the guide face for raising a temperature of the printing medium placed on the guide face; and a temperature raising preventing part (300, 400, 500, 575, 601, 602) which is provided between the placing face at a position facing the printing target region and the guide face of the guide part and prevents a portion of the printing medium, which is extended to the feeding-out side by a predetermined length from the printing target region where the ink is ejected from the printer head, from being heated by the printing medium temperature raising means, characterized in that the platen is structured of a main platen, a front platen, an after-heater and a groove part and a stepped part is provided between the main platen and the front platen which are physically separated from each other; the main platen is provided with suction holes in the support face of the main platen that supports the printing medium; and a decompression chamber is provided in the lower part of the suction holes so as to be capable of being set in a negative pressure. a platen having a placing face on which a printing medium in an elongated sheet shape is held; a printing means which is provided with a printer head that is oppositely disposed to the placing face of the platen and that ejects ink to a printing target region of the printing medium to perform printing and in which ink is ejected while the printer head is relatively moved to the printing medium that is placed on the placing face of the platen to perform printing on the printing medium; a printing medium feeding means which feeds the printing medium that is placed on the placing face of the platen out from the platen depending on the printing by the printing means; a front platen which is provided on a feeding-out side where the printing medium is to be fed out with respect to the platen and which is provided with a guide face on which the printing medium having been fed out from the placing face of the platen is placed and held; a printing medium temperature raising means which heats the guide face for raising a temperature of the printing medium placed on the guide face; and a temperature raising preventing part (300, 400, 500, 575, 601, 602) which is provided between the placing face at a position facing the printing target region and the guide face of the guide part and prevents a portion of the printing medium, which is extended to the feeding-out side by a predetermined length from the printing target region where the ink is ejected from the printer head, from being heated by the printing medium temperature raising means, characterized in that the platen is structured of a main platen, a front platen, an after-heater and a groove part and a stepped part is provided between the main platen and the front platen which are physically separated from each other; the main platen is provided with suction holes in the support face of the main platen that supports the printing medium; and a decompression chamber is provided in the lower part of the suction holes so as to be capable of being set in a negative pressure.