Shutter for magnetic disk cartridge

In a magnetic disk cartridge including a casing having a magnetic head access window, a disk shaped magnetic media rotatably housed in the casing, and a shutter adapted to be slidably mounted on the cartridge casing to selectively open and close said magnetic head access window and a torsion spring in the casing including a shutter engaging portion extending generally perpendicularly to the plane of said magnetic media, wherein the improvement comprises a guide member formed in said shutter including a notch portion for engagement with said shutter engaging portion of the torsion spring, said guide member including a guide portion extending generally parallel to the plane of said magnetic media and perpendicularly to said shutter engaging portion of the torsion spring, said guide portion being located adjacent said notch portion and positioned to engage the engaging portion of the torsion spring when the shutter is slid into the casing to guide said engaging portion of the torsion spring into the notch position, said guide portion facing said engaging portion of the spring when the shutter is slid into the casing and being slanted to incline at an angle to the sliding direction of the shutter, said engaging portion of the torsion spring engaging said guide portion when it is being fitted to the case, so as to guide said engaging portion toward said notch portion to be reliably retained by said notch portion.