Abstract: An exhaust gas processing conduit includes a main pipe and a purge pipe. The main pipe has a first sidewall and a connecting port formed on the first sidewall. The purge pipe has one end connected to the first sidewall via the connecting port. The purge pipe has a second sidewall in contact with the first sidewall at an oblique angle. A gas provided by the purge pipe is injected along the first sidewall and into the main pipe so as to guide the gas flowing along a spiral route at the oblique angle. In addition, a manufacturing apparatus and a gas flow guiding method thereof are also disclosed in the invention.