Provided is a sub-muffler which needs no heat resistant material such as SUS, and which can keep its durability and sound absorbing performance even when the sub-muffler is exposed to various corrosive components in the exhaust gas. At the same time, accomplished is a low-cost manufacture, which is a challenge that sub-mufflers and sound absorbing materials commonly face. Disclosed is a sub-muffler in which a perforated exhaust pipe is arranged, and caps and an out pipe are arranged outside the perforated pipe. Sound absorbing materials are filled in the space between the perforated exhaust pipe, and the caps and the out pipe. The sub-muffler is characterized in that, among the sound absorbing materials, at least part of the sound absorbing material of the perforated pipe side is a basalt fiber for high temperature.