Apparatus and method for purifying exhaust gas in an engine

The apparatus improves regeneration efficiency of a diesel particulate filter that traps particulate matter, reduces pressure loss caused by the filter, and benefits space of a vehicle. Therefor, the DPF (11) that traps particulate matter having a large diameter is connected to or close to an exhaust manifold (9a) in an engine (1), and the DPF (12) that traps particulate matter having a small diameter is disposed in an exhaust pipe (9b) downstream of the exhaust manifold (9a) and at a location away (under a vehicle floor) from the exhaust manifold (9a).