A recording tape cartridge has a case rotatably accommodating a single reel on which a recording tape is wound, an opening formed in portions of a front surface and a side surface adjacent to a corner portion of the case, and a door opening and closing the opening by rotating. The opening is for pulling-out of a leader member attached to an end portion of the recording tape. The door is structured so as to be able to cover the corner portion of the case including a portion of a top surface and/or a bottom surface when the door closes the opening.