A heat exchanger includes a plurality of flat tubes in which a fluid flows, and a plurality of fins each of which is connected to flat surfaces of adjacent tubes to increase a heat exchange area on a side of air flowing outside of the tube. The fin includes a plate portion having a plate surface, and fin protrusions protruding from the plate surface of the plate portion. The fin protrusions are provided to be spaced from the flat surface of the tube by a predetermined distance. A flow resistance portion is provided to protrude from the flat surface of the tube toward outside by a protrusion dimension that is equal to or larger than the predetermined distance.