To obtain a plate type evaporator using a plurality of heat transfer plates for transferring heat from a heating fluid to a liquid being evaporated in which pressure loss in the flow of the heating fluid and the liquid being evaporated is reduced and the ratio of area available for heat exchange to the entire surface area of the heat transfer plate is increased.

Two heat transfer plates 7 are superposed to form a first heat exchanging chamber 8 for passing heating fluid between. An opening to the first heat exchanging chamber is made in one peripheral side and both heat transfer plates are welded at other sides to constitute a unit plate body 6. A plurality of unit plate bodies are juxtaposed between respective unit plate bodies to form a second heat exchanging chamber 10 for passing a liquid being evaporated.