Plate heat exchanger

A plate heat exchanger (1) comprising a stack of heat transfer plates (2) provided between two end pieces (3, 4) and each having an essentially plane extension, each end piece (3, 4) having an inner surface facing said heat transfer plates (2) and an outer surface (10, 14, 22) facing away from said heat transfer plates (2) and extending from one side to another of the end piece (3, 4), the plate heat exchanger (1) being compressed by means of at least one member (11, 18, 24) extending around the end pieces and the heat transfer plates in such a manner that said member abuts said outer surface (10, 14, 22) of each end piece (3, 4) in order to prevent the retreat of the end pieces from each other, wherein said outer surface (10, 14, 22) of each end piece (3, 4) is continuously curved from said one side to another in such a manner that the end piece has a convex shape in a cross-section along a first plane (Y, Z) crossing said sides and being perpendicular to the essentially plane extension of the heat transfer plates (2) and the curved outer surface (10, 14, 22) in the proximity of an edge between said inner surface (9) and said outer surface (10, 14, 22) is shaped in such a manner that a tangential plane (X, Y) of said outer surface is essentially perpendicular to the essentially plane extension of the heat transfer plate (2).