A heater for heating a moving sheet material by contact therewith is used, for example, in electrophotographic apparatus for fixing toner to printing paper. The heater comprises an insulating substrate formed with a striplike heating element on its upper surface, and a support plate for supporting the substrate. A higher heat preserving property is given to the opposite end portions of the heating element than to a longitudinal intermediate portion thereof to thereby compensate for a temperature reduction at the element end portions and make the heating element uniform in temperature over the entire length thereof.