A cartridge case 1 for a magnetic tape cartridge comprises a cartridge case 1 consisting of a lower half 2 and an upper half 3. The lower half 2 is provided with retaining ribs 71 each having a retaining slanted surface 71a such that a plate-like cartridge memory 7 is positioned on the retaining slanted surfaces 71a with its one side 7d lowered and is obliquely supported with respect to a bottom plate 28 of the lower half 2. The upper half 3 is provided with supporting members for supporting various non-resilient constituent parts positioned on the lower half 2 and including the cartridge memory 7. The upper half 2 is provided with a stopper rod 77 such that when the upper half 3 is assembled with the lower half 2, the stopper rod 77 reaches a cartridge memory-rising region before the supporting members contact with the non-resilient constituent parts on the lower half 2.