A rotary particle sensor assembly and an air cleaner having the rotary particle sensor assembly are disclosed. Particularly, in the present invention, regardless of the orientation of the air cleaner, the rotary particle sensor assembly can always be oriented in the direction of gravity. The rotary particle sensor assembly includes a particle sensor, which measures the pollution level of air drawn into the air cleaner. The particle sensor is supported in the air cleaner so as to be rotatable using a rotating shaft and has a weight at a predetermined position. Thus, the particle sensor can always be oriented in the direction of gravity by the weight regardless of the orientation of the air cleaner. Therefore, the present invention ensures the accuracy of measurement of the pollution level of air.