Process for producing polyolefin resin composition

The process for producing a polyolefin resin composition according to the present invention has a mixing step of melt-kneading a plurality of polyolefin ingredients having intrinsic viscosities different from each other to prepare a mixed fluid; and a filtering step of introducing the mixed fluid into a filter device having a main body section having a flow passage through which the mixed fluid is transferred and a sintered metal filter disposed in the flow passage of the main body section of the device and forcing the mixed fluid to pass through the sintered metal filter so that the filtration rate of the mixed fluid will be in a prescribed range. The sintered metal filter is fixed to the main body section of the device while keeping a section where the edge of the sintered metal filter abuts with the main body section of the device hermetically sealed in the above filter device.