The invention relates to an electrical heating apparatus having a flat heating block which is kept in a casing having oppositely disposed frame openings and comprises a parallel layer with a dissipating element and a heat generating element. In order to simplify assembling process, the heat generating element has assembly elements protruding outside the heating block on the side of terminal surface, and assembly element accommodating seats belonging to assembly elements are formed on the casing. Assembly elements and belonged accommodating seats of different heat generating elements are formedso that the heat generating element can not be interposed form an arbitrary position.