PURPOSE: To perform efficient operation reduced in energy loss by taking the difference between the output of a gas sensor and that of a dust sensor and operating a ventilating function part by a differential amplifying control circuit when said difference reaches set difference or more.

CONSTITUTION: In the constitution having a cleaning means 5, an air cleaning part 3 equipped with a circulating blower 8 and a ventilating function part 4, a gas sensor 6a detecting the gas concn. of the air in a room and a dust sensor 6b detecting the concn. of dust are provided to a region 6c which is in contact with the air in the room atmospherically. The difference between the output of the gas sensor 6a and that of the dust sensor 6b is taken and, when this difference reaches set difference or more, the ventilating function 4 is allowed to function by a differential amplifying control circuit. As a result, efficient operation reduced in energy loss can be carried out.