The present invention relates to a cartridge and a printing apparatus, and provides a new method capable of coping with incorrect installation of a cartridge. An ink cartridge (200) has a label portion (210) on a wall surface of one periphery of a case (202) forming an ink accommodating unit. The label unit (210) has a lamination structure in which a plurality of layers with different properties and states are laminated, and includes an optical functional layer (213) that allows light (first wavelength of light) with a predetermined wavelength to pass and an optical reflective layer (212) that reflects the first wavelength of light, and the optical reflective layer (212) is a surface side of the case (202). When the optical reflective layer (212) is heated from a thermal head (102) of a heating unit (100) directed to the label portion (210), the optical reflective layer (212) irreversibly raises absorptivity of the first wavelength of light with respect to a received range.