A manufacturing method for a muffler includes: a trimming step, of cutting out a dogleg shaped muffler body member; a bending processing step of processing the muffler body member into a tube by advancing the muffler body member between an upper roller and a lower roller of a bending machine while adjusting an advancing direction with a guide and by changing a relative position of the upper roller and the lower roller; a first joining step of joining two ends of the tubularly-processed muffler body member in a long side direction; an insertion step of inserting an inner structural member into the inside of the tubularly-processed muffler body member; a second joining step of joining caps to opening portions of the tubularly-processed muffler body member; and a third joining step of joining an air intake joint and an exhaust pipe to the sealed muffler body member.