PURPOSE: To improve heat transfer performance by a method wherein bead patterns having angular change are provided on the upper and lower distributing surfaces so that the pressure loss difference due to the angular difference between the beads offsets the pressure loss difference due to the distance difference of flow passages.

CONSTITUTION: Efflux and influx ports of heat-exchange fluid 10a, 10b, 10c and 10d are formed at the four corners of each of heat transfer plates 8 and 9. The distributing surfaces 11a and 11b are formed at the upper and lower parts facing to the ports 10a, 10d and 10b, 10c of the plate 8, while the distributing surfaces 12a and 12b are also formed at the upper and lower parts facing to the ports 10a, 10d and 10b, 10c of the plate 9. The beads on the distributing surfaces 11a, 11b, 12a and 12b are formed so as to diverge from the ports 10a, 10b, 10c and 10d towards heating surfaces 13 and 15. In other words, the beads have angular change with respect to the ports 10a, 10b, 10c and 10d by forming the beads radially from one point lying on the center line of the width of the plates 8 and 9.