An exhaust gas purification device with a first exhaust pipe section for leading exhaust gas discharged from an engine, a second exhaust pipe section having in a side section on an upstream side thereof an opening section for introducing exhaust gas from the first exhaust pipe section, the second exhaust pipe section being connected at a side section thereof to the first exhaust pipe section so that flow of exhaust gas therein becomes a swirl flow and having provided on a downstream side thereof a post-processing device, and a reduction agent supply device provided at an upstream end of the second exhaust pipe section. The opening section is formed so as to include at least a first tilted side extending in a direction tilted relative to an axis of the second exhaust pipe section.