A plate type heat exchanger comprises a plurality of plates stacked on one another.
Each of the plates has a seal portion, which is provided on an outer peripheral
portion of the plate and with an interior of which inflow and outflow ports of
heat exchanging fluids are communicated, and heat-transfer surface elements formed
in a mountain-shaped manner in a thicknesswise direction of the plate and arranged
to form flow passages within the seal portion. The heat-transfer surface elements
are in the form of a quadrangular pyramid having flat top. The seal portion has
flat portions on outer peripheral portions of the flow passages to define a bottom
surface, and mountain portions, which extend upright from the flat portions and
of which tops are formed to be flat in shape.
