An automotive seat with a heating device provided therein, in which a trim cover assembly is integrally affixed over a foam cushion member, comprises a recessed portion formed at the rear of the cushion member, a block member removably inserted in the recessed portion, and a heating device secured on the block member. With such structure, the heating device is embedded in the cushion member such that it is interposed between those recessed portion and block member. Both cushion and block members are further supported on a frame and support member provided in the seat.