An ink paper cassette has ink paper, a supply shaft for supplying the ink paper, a take-up shaft for winding the ink paper, a front connecting portion for rotatably supporting first ends of the supply and the take-up shafts and a rear connecting portion for rotatably supporting second ends of the supply and the take-up shafts. The ink paper cassette is to be loaded into a printer. The printer performs thermal prints of characters and/or pictorial images onto a transfer paper with the ink paper loaded in the ink paper cassette. The front connecting portion has a depth so greater than that of the rear connecting portion that the front connecting portion is brought into abutment with a front face of a printer mechanism, whereby preventing the ink paper cassette from being loaded into the printer.