A label sheet for electrophotography, constituted of a label base member and a separator base member both made of resin film, and an image forming method with use thereof. Difference of thermal shrinkage rates in an MD direction between the label body and the separator of the label sheet after heat treatment for 5 minutes at 150° C. is in the range of −0.3% to 0.1%. Stiffness E·t3, a function of a tensile elasticity rate E (N/mm2) of the separator at 135° C. and thickness t (mm) of the separator at 23° C, 50% R.H., is 0.21 N·mm or more. Occurrences of winding around a fuser and marks of winding are suppressed, curls are small, and toner cracks do not appear even if printed matter is left in conditions of high temperature and high humidity.