An exhaust gas detoxifying system includes a catalytic converter in the exhaust system of an engine to detoxify exhaust gas. An air conditioner includes a compressor which is driven by the engine, and it performs air conditioning of the vehicle interior based on a refrigeration cycle. The operation of the air conditioner compressor is restricted depending on the degree of necessity of air conditioning, which is calculated from the difference between a vehicle interior temperature and a target temperature, if the catalytic converter exhaust gas detoxification performance is expected to deteriorate during accelerating or heavy-load operations of the engine.