Exhaust gas purification device

An exhaust gas purification device that oxidizes or reduces pollutants contained in an exhaust gas by bringing the exhaust gas resulting from combustion into contact with a catalyst, comprising:

• a flow path for flowing the exhaust gas therethrough in which the catalyst is formed at least on an inner surface thereof,
• wherein the flow path includes an inner wall surface extending in a flowing direction of the exhaust gas, and
• a length of the flow path as a length of the inner wall surface in the flowing direction of the exhaust gas is set to a length calculated using the following equation
• Le
• =
• {
• dH
• /
• 9.28
• ·
• √
• (
• ρ
• ·
• u
• /
• μ
• )
• }
• 2
• or shorter, where dH is a hydraulic diameter (m), ρ is a density (kg/m3) of the exhaust gas, u is a flow rate (m/s) of the exhaust gas, and μ is a viscosity (Pas) of the exhaust gas.