In a magnetic tape cartridge (1) having a metal plate (25) at the central portion of the bottom surface of a reel hub (21) with a reel gear (24) being defined around its periphery, the metal plate (25) is disposed in a manner such that the outer periphery of the metal plate (25) is positioned under the inner facing surface of the reel gear (24). As a result, occurrence of a sink mark during molding at a portion where the reel gear (24) is formed and deformation of the reel hub (21) due to tape widing tention are prevented.