The present invention relates to a polymer film comprising a polymer having liquid crystallinity, having a number-average molecular weight in terms of polystyrene of 10.sup.3 to 10.sup.8 and having an electron mobility or hole mobility of 10.sup.-5 cm.sup.2/Vs or more, and having a film thickness in the range from 1 nm to 100 .mu.m. This polymer film can be used for various polymer film devices such as an organic transistor, organic solar battery, optical sensor, electrophotographic photoreceptor, spatial light modulator, photorefractive device and the like.