Combined apparatus for heating, cooking, grilling and defrosting of foods of various kind, depending on the kind of foods to be treated from time to time and the duration of the foods treatment foreseen by each user of the same apparatus, comprising substantially a box-like covering and containing envelope made of metal or also of other solid material and with parallelepiped shape, or other suitable geometrical shape, in the lower part of which there are mounted some supporting feet, which may be adjusted or not adjusted in height, and suitable for being laid and/or installed on to supporting surfaces of various type of the room into which the apparatus is installed, the apparatus comprising moreover an upper cover, hinged to the box-like envelope near its upper and back end portion and which can be actuated either manually by the user from the front part of the same envelope, or with an automatic opening at the end of the food cooking, the apparatus also comprising at least a control board for controlling the carrying out of the different operative programs desired from time to time and selected by means of selector means, depending on the type and the quantity of foods to be hot treated, and for regulating the power, the temperatures and the times of the desired treatments, said control board being connected to the apparatus electric circuits, together with heating elements of foods and temperature detecting means for heating said heating elements, the envelope also comprising at least an inner treatment room for the hot treatment of foods, for introducing the foods to be hot treated from time to time, which is accessible or not accessible by closing or opening said upper cover, said inner room being insulated thermally and adapted to be heated singularly either through said heating elements or microwave generating means (68, 69), or the combined action of said heating elements and said microwaves generating means (68, 69), said heating elements being included into at least a stationary upper plate, weighing means being provided and connected operatively with said control board for detecting the weight of foods and providing for through the same control board the carrying out of each operative program respectively selected and the heating duration of each food, depending on the type and the weight of the food to be treated from time to time, characterized in that said cover is displaceable from a lowered closed position, in which the same cover is aligned in the horizontal direction with the remaining upper surface of the envelope, and the interior of the envelope cannot be accessible from the outside, to a raised opened position thereof, in which the cover is upset upward and arranged in the vertical position thereof almost orthogonal with respect to the remaining upper surface of the envelope and the interior of the envelope is accessible from the outside, said cover being formed by a first flat cover portion and by a second flat cover portion, joined to the first cover portion at its front end portion, which is folded orthogonally frontwards with respect to such flat portion, and this second cover portion is made with a smaller surface with respect to the surface of said first cover portion, the upper cover being made with an external wall and an inner wall enclosing an insulating material, such as for example any insulation withstanding the high temperatures, said upper cover being also dimensioned in a manner that into its lowered position said first cover portion be adapted perfectly on to the entire horizontal upper edge of said inner room said heating elements being included also into a movable lower heating plate, which cooperates with said weighing means and which may be actuated by means of powered transmission means (42, 46, 47, 49, 50), controlled by said control board, into different adjustment positions in height, depending on the size and the type of food to be hot treated, for enclosing the food between said two heating plates (35, 36).