Abstract: The invention relates to a plate heat exchanger, which comprises a plurality of plates (1) arranged to the side of each other, each plate consisting of two metal sheets (2,3), which are welded one to the other along two parallel edges and have longitudinal bulgings in parallel with said edges. The invention has the object to produce a plate heat exchanger where the medium flowing within the plate is guided in a direction in parallel with the extension of the bulgings and back in the same direction. Each plate (1) is formed with a turning zone in that the bulgings in pairs meet in such a manner, that in the sheet plane two outermost bulgings meet along a semicircle line, thereafter the two bulgings next to the outermost ones, a.s.o., and the number of bulgings is an integer number.