A high molecular electret film which comprises an electret film of a blend of a poly(2,6-dialkyl-1,4-phenylene oxide) consisting of a recurring unit represented by the following general formula (1), ##STR1## wherein R is an alkyl group having not more than 4 carbon atoms, and a styrene resin. The electret film exhibits vary favorable electric charge-retaining property and favorable adhesiveness to metals. The film is very effectively used for a developing sleeve in an electrophotographic apparatus, for a cleaning device, for a transfer device, etc. and exhibits desired effects stably and for extended periods of time.