Abstract: A device for purifying exhaust gas of a diesel engine is equipped with a continuously regenerating diesel particulate filter (DPF) that uses a catalyst. A second continuously regenerating DPF of a small capacity is disposed in a by-path that by-passes the exhaust gas passage of the diesel engine equipped with the continuously regenerating DPF. The particulate matter (PM) is trapped by the second continuously regenerating DPF in the region of low exhaust gas temperatures. A homogeneous charge compression ignition is executed by advancing the timing for injecting the fuel into the cylinders to reduce the formation of PM. Therefore, the PM can be trapped to a sufficient degree despite the second continuously regenerating DPF has a small capacity. To suppress the formation of NOx, further, the cooled exhaust gas is recirculated into the cylinders and, besides, a urea-added SCR catalyst is disposed in the exhaust gas passage to reduce and decompose NOx in the exhaust gas to further reduce NOx.