Heat exchanger, gap expansion jig of heat transfer tube, and method of disposing vibration suppression member

There is provided, for example, a heat exchanger which can suitably suppress vibration of a plurality of heat transfer tubes. The heat exchanger includes: a plurality of heat transfer tubes which is arranged and provided with predetermined gaps; and a plurality of second vibration suppression members 14B which is provided in the gaps and is provided on both sides sandwiching each of the heat transfer tubes 5, and one second vibration suppression member 14B and the other second vibration suppression member 14B of a plurality of second vibration suppression members 14B are provided at different positions in an axial direction of the heat transfer tubes 5 sandwiching the heat transfer tubes 5, the one second vibration suppression member 14B is provided pressing the heat transfer tubes 5; and the other second vibration suppression member 14B is provided pressing the heat transfer tubes 5 from an opposite side of the one second vibration suppression member 14B.