An exhaust gas purification device (1) comprising a main exhaust passage (2) and a branch exhaust passage (3) connected to an exhaust passage (100) on the engine side; shutoff valves (4A) and (4B) capable of shutting off exhaust gas at the exhaust inlets (2a) and (3a) of the main exhaust passage (2) and the branch exhaust passage (3); a nitrogen oxide adsorbing material (5); an adsorbed material detachment unit (6), having an air nozzle (61); and a combustion device (7) including an air nozzle (71), a fuel nozzle (72) and an ignition plug (73), wherein the exhaust gas from the exhaust passage (100) on the engine side is discharged directly from the exhaust outlet (3b) of the branch exhaust passage (3).