A heat exchanger finned tube 10 for use in fabricating a heat exchanger 1 useful as the evaporator for refrigerators or the like wherein a hydrocarbon refrigerant is used. Two tube insertion holes spaced apart from each other are formed in each of plate fins 12, and two straight tube portions 11a of a hairpin tube 11 are inserted through the respective holes of each plate fin to arrange the plate fins 12 in parallel into a plurality of fin groups 13 spaced apart on the straight tube portions 11a longitudinally thereof. The hairpin tube 11 is enlarged with use of a fluid to fixedly fit the plate fins 12 of each tin group 13 around an enlarged tube portion 14 of the hairpin tube 11 and provide a finless part 19 between each pair of adjacent fin groups 13 on each of the straight tube portions 11a. A restrained small-diameter portion 15 is provided in each of the finless parts 19 of each straight tube portion 11a. The heat exchanger 1 fabricated using the finned tube 10 exhibits the desired refrigeration performance with the leakage of refrigerant diminished.