To provide a dust collection bag which keeps ability suppressed in trapping dust particles is prevented.

The dust collection bag 1 is formed in a bag shape wherein a front face 2 and a rear face 3 are superposed by joining the edges of a pair of sheet-shaped members 2A and 2B to each other, is accommodated inside a dust collecting machine in which a dust-collecting port opens, is provided with a dust particle suction port connected to the dust collection port, at a position near one end of the front face, and catches the dust particles drawn in from the dust collection port, through the dust particle suction port. At least one fold 6 extending from the end that faces the position near the one end to the opposite end is formed on the rear face to allow the space between the front face and the rear face to be widened by drawing the fold toward the outside of the rear face inside the dust collecting machine.