Abstract: The recording medium cartridge accommodates a recording medium such as a magnetic tape, a optical and/or magnetic disk, or the like in a cartridge body having an upper half and a lower half. A non-contact type memory device storing information, for example, given when producing the cartridge is provided in a reel of at least one of upper and lower flanges of a tape reel or on a surface facing to the tape winding surface of the body in the cartridge accommodating the tape reel wound with the tape, or in a recessed portion formed in at least one of a bottom surface of the lower half and an upper surface of a slider or in the slider in the cartridge having the slider, or in a transparent window of the body. A part of at least one of the upper and lower halves that corresponds to the memory device may be notched. The memory device may be welded together when fitting other members.