Disclosed is a dust-collecting filter of a vacuum cleaner which can be reused after emptying and washing off the contaminant filled inside the filter. A dust collecting filter comprises a first case member with an air inlet hole connected through with an air inlet port of the dust collecting chamber, a second case member with a plurality of air discharge holes formed on the side for forming paths for discharging air flown in through the air inlet hole, the second case member connected with the first case member to form predetermined space in between the first case member and the second case member, and a contaminant separating means disposed on air discharge path of the predetermined space for separating and collecting contaminants from air passing the air discharge path and being discharged through the air discharge hole. The first case forms a cylinder and has a plurality of groove portions on the side, and the second case forms a cylinder and has a plurality of resilient plates with hooks for hooking on the groove portions whereby the first case member and the second case member are selectively separatable.