Dust collecting unit of vacuum cleaner

The invention discloses a dust collecting unit for a vacuum cleaner, which comprises a first cyclone device for filtering foreign bodies in air for the first time, a second cyclone device for filtering the foreign bodies in air passing the first cyclone device 240 for the second time. The invention is characterized in that: the second cyclone device comprises a plurality of small cyclone sections of different diameters guiding air to flow in helix and a plurality of guiding tubes positioned in the small cyclone sections and used for guiding air flow upward. The invention has the advantages that: with the availability of double filtering foreign bodies in air sucked outside through the flow of cyclone, enhances the air purify capacity of the vacuum cleaner, namely the advantage of filtering foreign bodies; besides, with the plurality of small cyclone sections of the different diameters, the invention can effectively utilizing the internal space of the dust collecting unit; together with the small cyclone secti