A method for producing a fiber-reinforced resin composition including supplying a plurality of fiber bundles (1) into an impregnation chamber (10); supplying a molten thermoplastic resin from a resin flow inlet (4) into the impregnation chamber (10) so that the amount of the resin flow is almost the same on on each side the direction perpendicular to the fiber bundle (1) progress direction; contacting the molten thermoplastic resin with the fiber bundles (1) to impregnate the fiber bundles (1) with the molten thermoplastic resin; and withdrawing the fiber bundles (1) impregnated with the molten thermoplastic resin from the impregnation chamber (10).