A recording tape cartridge having: a case which accommodates a reel for a recording tape; an opening formed at a corner portion of the case; and a door which has a bent portion formed in a substantial L-shape in plan view, and opens and closes the opening, wherein the plate thickness of the bent portion in a direction in which the door rotates is larger than that of the door, and a stepped portion is formed at the further end side from the bent portion of the door, wherein also the case includes a first abutting portion which abuts the door when it is closed, and second abutting portions which abut the end surface of the bent portion at a door distal-end side thereof, and the inner surface of the bent portion, when the closed door is further deflected in a direction of closing the opening.