A heat exchange plate having a pattern of irregularity is combined with the other plates to constitute a heat exchanger. The plate has main and intermediate protrusions. The main protrusions have a quadrangular pyramid shape with a top, first and second pairs of side surfaces. The first and second pairs of side surfaces face each other in the first and second directions. The main protrusions are aligned in these directions so that these pairs of surfaces of the main protrusion face the corresponding surfaces of adjacent protrusions. The intermediate protrusion is placed between adjacent main protrusions and has opposite foot portions and a head ridge placed between them. The foot portion is placed in a lowermost position at which ridgelines of the adjacent two main protrusions intersect. The head ridge is placed in a level higher than the foot portions, but lower than the top of the main protrusion. |