A reel of a recording tape cartridge has a reel hub formed in a shape of a hollow cylinder; an annular reel gear; an upper flange; a lower flange; and a reel plate. A reel gear is provided coaxially at an outer surface of a floor of the reel hub, and meshes with a driving gear of a rotating shaft of a drive device. A reference surface is provided integrally at an outer side of the floor. The upper flange extends integrally toward a radial direction outer side from an open end of the reel hub. The lower flange is mounted to a floor side end of the reel hub, and opposes the upper flange. The reel plate is fixed to the outer surface of the floor, and is attracted by a magnet of the rotating shaft without being contacted by the magnet.