A muffler is capable of stably supporting the catalytic converter in a muffler box with a pair of partitions. The muffler box includes first and second box halves joined together with open surfaces thereof abutting each other, and first and second partition plates interposed between the first and second box halves and overlapping each other to separate inside of the muffler box into first and second silencing chambers and define a third silencing chamber between the first and second partition plates, one end opening of a cylindrical holding tube housing and holding the catalytic converter is connected to the exhaust inlet pipe, the pair of partition plates support the holding tube in such a way as to wrap an outer peripheral surface thereof, and another end opening of the holding tube is communicated with the exhaust outlet pipe through the first, second, and third silencing chambers in this order.