A tape cartridge detachably mounted in a tape printing apparatus, which has a printing head portion, a drive shaft, and a base convex portion that includes a pedestal erectly disposed on a mounting base and a convex portion erectly disposed on and integrally formed with the pedestal, includes a tape roll and a core shaft that has an outer circumferential face that rotatably supports the tape roll and an inner circumferential face formed into a stepped cylindrical shape formed by a concave portion and a depressed portion which has a diameter larger than that of the concave portion. A spring is installed into the concave portion. When the tape cartridge is mounted in the tape printing apparatus, the convex portion is inserted into the concave portion and presses the spring to release an inverse rotation prevention of the tape roll, and the depressed portion receives the pedestal.