Abstract: The present invention provides a polyolefin film for electric insulation which is obtained by using a uniaxially drawn film of crystalline polyolefin, in which intramicrofibril and intermicrofibril amorphous parts of the uniaxially drawn film are impregnated with a low loss insulation oil, and which simultaneously satisfies the following conditions:(i) a tensile Young's modulus of the film impregnated with the insulation oil is 2.times.10.sup.4 kg/cm.sup.2 or higher;(ii) a dimensional change (change in length) of the uniaxially drawn film in the insulation oil at 100.degree. C. is within a tolerance of .+-.2%;(iii) a ratio of a long period at room temperature of an ether extraction residue of the uniaxially drawn film to a long period thereof before ether extraction is within a range of 0.900 to 0.998; and(iv) a dimensional increase of the ether extraction residue in the insulation oil at 100.degree. C. is 0.1% or higher.