A coupling structure of a heat transfer plate and a gasket for use in a plate type heat exchanger. The heat transfer plate has a groove for receiving the gasket. The coupling structure includes a protrusion formed at a first surface of the gasket, a recess formed at a second surface of the gasket having the same shape as the protrusion, and an inverted U-shaped prominent portion formed at the bottom of the gasket groove of the heat transfer plate. A prominent portion of the heat transfer plate is tightly inserted into the recess of the gasket, and the protrusion of the gasket located under the prominent portion of the heat transfer plate is inserted into a recessed internal space of the prominent portion.