A filter cleaning apparatus 1 is a device designed exclusively for cleaning a cartridge filter used in a fluidized bed granulator. A cleaning liquid 10 is reserved in a processing container 2. In the processing container 2, a cartridge filter 3 is placed in the state of being immersed in the cleaning liquid 10. The filter 3 is so disposed as to be capable of rotating around a rotational axis line O that is substantially horizontal in the processing container 2. Air nozzles 8 are disposed below the cartridge filter 3. An uplift pressure of bubbles rising out of the liquid into the atmosphere is added to a bubble flow BF jetted from the air nozzles 8. As a result of the synergic effect of the jet pressure of the bubble flow BF and the uplift pressure, the filter 3 rotates in an efficient way, leading to an improvement in cleaning efficiency.