Abstract: A plate-type heat exchanger is provided with a sealing device positioned between pairs of adjacent plates (12). Said device comprises a gasket (11) placed inside of a suitable peripheral groove (21), as well as a plurality of protuberances (10) projecting from a peripheral area (13) of said gasket (11) towards a peripheral area of the plate (12) to which said device is coupled. Said heat exchanger is provided with a plurality of recesses (19) having a predetermined shape and placed along the peripheral edge of each plate (12) constituting said heat exchanger; furthermore, each protuberance (10) has a shape which is conjugated to the shape of the corresponding recess (19) so that said protuberance (10) can interact with said corresponding recess (19) in such a way as to insert an edge of said recess (19) inside of a groove (16) provided in each protuberance (10).