PURPOSE:To ensure the accurate positioning between a disk type recording medium and a recording/reproduction head by drilling a head inserting hole through upper and lower cases and providing a reinforcement member to the side area of a case separated by a head inserting hole. CONSTITUTION:The diameter (d) of the 1st reinforcement member 24 is smaller than the thickness S of a cartridge case 1 and preferably equal to or smaller than the thickness of a disk type recording medium 2. The member 24 is bridged over the recess grooves 11 and 11a at the junction part between upper and lower cases 5 and 6. While the 2nd reinforcement member 25 is made of rigid synthetic resin equivalent to the synthetic resin material used to both cases 5 and 6. The thickness of the member 25 smaller than the thickness S of the case 1 and preferably equal to or smaller than the thickness of the medium 2. Then the member 25 is bridged over the recess parts 12 and 12a at the junction part between both cases 5 and 6.
