To collect sucked dusts in a cleaning mechanism cleaning the internal components of the indoor unit of an air conditioner by sucking action.

A prefilter cleaner 60 as the cleaning mechanism stored inside of the indoor unit 1 of the air conditioner 100 and cleaning the prefilter 30 of the indoor unit 1 includes a cleaner body 65 and a dust collecting filter 62. The cleaner body 65 has a cleaner casing 61 and a suction/exhaust fan 64. The cleaner casing 61 is formed with a suction port 61a and an exhaust port 61b. The suction/exhaust fan 64 is arranged inside of the cleaner casing 61 and generates an air flow sucked from the suction port 61a of the cleaner casing 61 and blown off from the exhaust port 61b. The dust collecting filter 62 is arranged upstream of the air flow from the exhaust port 61b and collects the dusts separated from the prefilter 30.