Exhaust gas purifying system for engine

The exhaust duct 28 of a direct-injection engine 1 is provided with three-way catalyst 32 and a lean NOx catalyst 33 are arranged in that order from the upstream side. Switching between a stratified combustion state at a stratified combustion region (I) of low revolutions speeds and low loads and a homogeneous combustion state of substantially the theoretical air/fuel ratio at a warm lambda =1 region (II) adjacent thereto with higher revolution speeds or loads, a first oxygen concentration sensor 30 is arranged upstream from the three-way catalyst 32, and when the engine 1 shifts from the stratified combustion region (I) to the warm lambda =1 region (II), the feedback control of the air/fuel ratio based on an output signal of that sensor 30 begins, and the target air/fuel ratio A/F is set to a range of 14.0