A first flow path A and the second flow path B are formed alternately between a plurality of heat transfer plates 1 arranged at predetermined intervals inner fin 2 is provided in the first flow path A and the second flow path B It was a plate heat exchanger, upstream each of the plurality of heat transfer plates 1, serving as the inlet of the second fluid into the inlet or the second flow path B of the first fluid into the first flow path a and the passage holes 20a, and a downstream-side passage hole 20b serving as the second fluid outlet of the outlet or the second flow path B of the first fluid from the first flow path a, the first flow path a and the second flow in each of the road B is plate-shaped rectifier plate 30 so as to partition between the upstream side passage hole 20a and the inner fin 2 is disposed, the rectifying plate 30, a first fluid or the second fluid passages having a plurality of openings 31, is adjusted opening area of ​​the plurality of apertures 31 as flow path resistance decreases as the distance between the upstream-side passage hole 20a is toward the far side from the near side in the rectifier plate 30 there.