Heat exchanger

The invention provides a heat exchanger. A heat exchanger is provided with: a base section including a first base flow path and a second base flow path through which a medium flows in a first direction; and a plurality of first heat exchange bodies connected to the base portion, positioned between the two target members, arranged in a first direction, and including a first flow path for circulating the medium in a second direction intersecting the first direction. The first heat exchange body includes: a front surface portion and a back surface portion formed by folding back the first film; a first outer edge joining part that joins the inner surfaces of the first films to each other along the outer edges of the front surface part and the back surface part; and a first division joining portion joining inner surfaces of the first film to each other to divide the first flow channel into a first downstream channel connected to the first base flow channel and a first backflow channel connected to the second base