Heat exchangers and heat exchanger unit

PROBLEM TO BE SOLVED: To provide a technique that enhances the performance of a heat exchanger composed of heat exchange tubes.SOLUTION: The heat exchanger (1) has a plurality of flat heat exchange tubes (2). The heat exchange tubes (2) have an internal flow channel (3) through which a first fluid flows. The plurality of heat exchange tubes (2) is arranged such that an external flow channel (8) through which a second fluid flows for heat exchanging with the first fluid is formed between the adjacent heat exchange tubes (2). The plurality of heat exchange tubes (2) is joined to each other at an inlet (3a) and an outlet (3b) of the internal flow channel (3). One of a pair of adjacent heat exchange tubes (2) is offset with respect to the other in a direction perpendicular to the arrangement direction of the plurality of heat exchange tubes (2).