A plate type heat exchanger is a plate type heat exchanger in which a first flow path through which a first fluid circulates and a second flow path through which a second fluid circulates are alternatively formed between a plurality of heat transfer plates, and an inner fin is disposed at least in the first flow path. Further, in the plate type heat exchanger, recessed grooves having a dimension smaller than that between fin sections of the inner fin are formed along a flow direction of the first fluid in an area of the inner fin that faces the heat transfer plate and on the heat transfer plate.