Heat transfer device of a stacked plate construction has a stacked plate construction consisting of alternately stacked flow duct plate units with flow duct openings and connection duct openings as well as connection cover plate units with connection duct openings provided such that two separate fluid flow systems are formed. The equal-sided connection duct openings overlap only by means of an interior portion with the equal-sided ends of the flow duct openings, whereas, by means of an exterior portion, while forming a respective connection conduit, they extend in the area outside the flow duct openings. This implements a compact plate stack construction with an optimal connection geometry for very low pressure losses.