To provide a dust collecting filter provided with a bellows part on the side of a side with which a support plate is engaged wherein the bellows part can be smoothly expanded when the filter is installed on an installation engagement part of a vacuum cleaner.

At least one side 9a of a support plate 9 is engaged with an installation engagement part of a dust collecting filter containing chamber in a vacuum cleaner, so a dust collecting filter 1 is installed. In this case, a protruded length S1 from the side 9a of the support plate 9 engaged to an edge 33 of a first bellows part 6a of a bag body 2 on which the support plate 9 is installed is set to be shorter than a protruded length to an edge 35 of a third bellows part 6c corresponding to a back surface 31 of the bag body 2. By thus composing the device, deformation degree of the first bellows part 6a at the installation engagement part can be reduced.