A magnetic disk cartridge has a case on which a transducer access rectangular opening is formed, a magnetic disk accommodated in the case, and liners partly welded to the inner surfaces of the case in order to clean the surfaces of the magnetic disk. The magnetic disk cartridge is characterized in that the liners are welded to the inner surfaces of the case through a welding pattern. The welding pattern comprises a discontinuous line extending along the edge of the liner and a straight line intersecting with the discontinuous line but not extending to overlay the effective magnetic recording area.