There is disclosed a heat exchanger tube for conducting refigerant in a heat exchanger. The inner surface of the tube has a convex portion having a broad tip and a plurality of inner fins. The area of the tip of the convex portion is larger than that of the tip of the inner fins. The height of the convex portion can be set at more than that of the inner fin. A heat exchanger according to the invention has a plurality of plate fins, each having a hole therein. Heat exchanger tubes pass through the holes of the plate fins. A method of manufacturing a heat exchanger comprises the steps of stacking a plurality of plate fins, each having a hole, with a predetermined space therebetween. Heat exchanger tubes are inserted through the holes. Then, the tubes are expanded to engage the plate fins. A refrigerating circuit utilizing a heat exchanger is also described.