An object of the present invention is to provide a polyolefin composition prepared by kneading a hygroscopic inorganic filler into a polyolefin, without substantially using an additive such as a dispersant or an antioxidant, the polyolefin composition having good dispersibility of the hygroscopic inorganic filler as well as excellent moldability. By kneading anhydrous magnesium sulfate as a hygroscopic inorganic filler into a polyolefin, without substantially adding an additive such as a dispersant or an antioxidant, and by setting the moisture content in the kneaded product to 0.1 wt % or less, a polyolefin composition having good dispersibility of anhydrous magnesium sulfate as well as excellent moldability can be obtained.