The present invention relates to a plate heat exchanger for simultaneously exchanging heat between two sets of fluids having different temperatures. The plate heat exchanger comprises a heat exchange element (2) comprising two plates facing each other so as to form a inner sealed space as a passage for a first fluid, and a plate surface of the plate serves as a heat transfer surface, and a fluid flowing along an outer surface of the plate is a second fluid. The plate heat exchanger comprises a heat exchange element (2′) comprising two plates facing each other so as to form a inner sealed space as a passage for a third fluid, and a plate surface of the plate serves as a heat transfer surface, and a fluid flowing along an outer surface of the plate is a fourth fluid. A plurality of the heat exchange elements (2) and a plurality of the heat exchange elements (2′) are alternately disposed in such a manner that the plate surfaces of the plates are opposed to each other and a predetermined gap is formed between adjacent the heat exchange elements. A communication pipe communicating with the inner spaces of the heat exchange elements (2) and a communication pipe communicating with the inner spaces of the heat exchange elements (2′) are formed on the plate surfaces of the heat exchange elements (2) and (2′) and integrally formed with the elements.