Method for producing resin composition

A method for producing a resin composition comprising:

• providing an extruder comprising:
• a cylinder having a main feed port and a side feed port downstream from the main feed port in an extrusion direction,
• a screw disposed inside the cylinder, and
• at least three kneading sections constructed by (i) a first element having kneading discs which are superposed and staggered at a phase angle greater than 0 degrees and less than 90 degrees and (ii) a second element which is a neutral kneading element,
• supplying a resin (A) to the extruder from the main feed port;
• supplying a fibrous filler (B) having a weight average fiber length of 1 mm or more to the extruder, a ratio of an amount of the fibrous filler (B) supplied from the main feed port and an amount of fibrous filler (B) supplied from the side feed port being from 1:4 to 1:0;
• melt-kneading the supplied resin (A) and the fibrous filler (B) to obtain a melt-kneaded material;
• and
• extruding the melt-kneaded material.