To solve a problem associated with conventional game machines that a reel drum consists of a reel drum body and a reel band and these items must be assembled together; therefore, an assembling process is involved without exception and this complicates the manufacturing process therefor.

Various patterns 12 are drawn on a thermoplastic resin sheet 10 so that the patterns are circularly arranged around a positioning hole 17 at the center. The resin sheet 10 is subjected to heat press forming. That is, the sheet 10 is heated and a die 30 having a projection 33 is pressed against the sheet 10 from beneath with the projection 33 aligned with the positioning hole 17. Thus, a cylindrical peripheral portion 13 with the various patterns 12 drawn thereon and a peripheral portion supporting portion 14 which supports and keeps the peripheral portion 13 in cylindrical shape are integrally formed. Flashes 18 are removed from the formed resin sheet 10 to shape the sheet. A projected portion 19 of the resin sheet 10 formed by the projection 33 is cut off, and thus a hole 15 into which the rotating shaft of a reel motor is inserted is formed in the center of the peripheral portion supporting portion 14. As a result, a reel drum 11 is formed.