Abstract: The method for manufacturing a fin-tube heat exchanger includes the step of expanding each heat transfer tube extending through a corresponding tube insertion hole of a heat transfer fin with a tube expander inserted in heat transfer tubes. The expanding step includes a first sub-step of expanding the tube expander in a radial direction of the heat transfer tube to a radially expanded state while the tube expander is at rest in a first predetermined region to be expanded inside the heat transfer tube to bring the first predetermined region to be expanded into close contact with the tube insertion holes; and a second sub-step of releasing the tube expander from the radially expanded state to a radially contracted state and moving the tube expander to a second predetermined region to be expanded inside the heat transfer tube. The first and second sub-steps are alternately repeated.