A polypropylene film which has a crystallite size of not more than 12.2 nm, the crystallite size being determined using Scherrer's equation from a full width at half maximum of the reflection peak from (040) plane of α crystal measured by a wide-angle X-ray diffraction method, and a volume resistivity of not lower than 6×1014 Ω·cm, the volume resistivity being calculated in accordance with equation I from a current value that is measured 1 minute after applying a voltage at a potential gradient of 200 V/μm in an environment at 100° C. Equation I: volume resistivity=[(effective electrode area)×(applied voltage)]/[(polypropylene film thickness)×(current value)].