A material-feeding device (14) includes a base (52), a material passage (54) formed on the base, at least one guide member (56, 58) provided in the material passage and having a material-guide surface (56a, 58a), a direction-correcting roller assembly (60) provided in the material passage, and a conveyor roll mechanism (62) disposed downstream of the direction-correcting roller assembly in relation to a material-feeding direction, for conveying a material along the material passage. The direction-correcting roller assembly (60) includes a pair of integrally rotatable polygonal rollers (76) having a common rotation axis oblique to the material-guide surface and a freely rotatable ball (78) opposed to the pair of polygonal rollers and elastically supported in an operative position closer to the polygonal rollers to define a gap between the ball and each of the polygonal rollers for allowing the material to be inserted into the gap when the ball is in the operative position. The direction-correcting roller assembly (60) holds the material between the pair of polygonal rollers (76) and the ball (78), and intermittently feeds the material toward the guide members (56, 58).