A dust collecting device includes a cylindrical filter, a backwash auxiliary member that is disposed at an end portion of the filter and of which at least a part is disposed in a cylinder of the filter, and an air current generation unit that generates a backwash air current that passes through the backwash auxiliary member and flows into the cylinder of the filter, in which the backwash auxiliary member includes a rectification unit that extends spirally in an axial direction of a center axis of the filter.