A cartridge for a recording medium and an image forming apparatus are provided. The image forming apparatus includes a housing, a printing unit disposed inside the housing, and having a thermal head with a heating element, and a cartridge for a recording medium, in which a recording medium wound in a roll shape is installed and which is provided to supply the recording medium to the printing unit, wherein the cartridge for a recording medium has a de-curl roller which guides the recording medium to be curved in a direction opposite to a winding direction, and is provided to be movable in a direction adjacent to the recording medium when the recording medium is supplied to the printing unit.