A visualization device for dust collection of a vacuum cleaner, comprising: a collecting unit mounted in a side of a transfer course of a flow of air generated by suction force of the vacuum cleaner for suctioning a dust to move at least a portion of suctioned air and dust in one direction; wherein a dust collecting unit is made of a transparent material having a first and a second vent (241, 243) disposed at a position different from each other to introduce the air, wherein the first and the second vent (241, 243) are formed in the dust collecting unit to communicate with each other, such that when operating the vacuum cleaner, said portion of suctioned air and dust is introduced into the inside of the dust collecting unit through the collecting unit; a discharge unit for guiding so that air and the suctioned dust passing through the dust collecting unit are discharged into the transfer course of a flow of air generated by the suction force of the vacuum cleaner, and a foreign material discharge means for forcibly discharging dust stacked in the inside of the dust collecting unit into the outside by sliding-moving the dust collecting unit by an operation of a user and by communicating the vents with each other, wherein the dust collecting unit includes a first housing forming an outer appearance, and a second housing disposed vertically at the inside of the first housing, wherein the foreign material discharge means includes the first vent formed in the first housing and introducing outer air into the inside of the first housing, the second vent, formed in position different from the first vent, the second vent being formed in the second housing and selectively communicating with the first vent,an elastic member for selectively allowing air communication between the first vent and the second vent by elastically supporting the first housing or the second housing, and a push-button connected to the first housing or the second housing, wherein when an external pressure is applied to the push-button, the elastic member is compressed and the push-button and the first housing are moved downward to allow the first vent and the second vent to be positioned on a same line, thereby allowing the foreign material discharge means to force the air to flow into the dust collecting unit for forcibly discharging the stacked dust, wherein when the external pressure to the push-button is released, the push-button and the first housing are returned to their initial positions by the elastic member. a collecting unit mounted in a side of a transfer course of a flow of air generated by suction force of the vacuum cleaner for suctioning a dust to move at least a portion of suctioned air and dust in one direction; wherein a dust collecting unit is made of a transparent material having a first and a second vent (241, 243) disposed at a position different from each other to introduce the air, wherein the first and the second vent (241, 243) are formed in the dust collecting unit to communicate with each other, such that when operating the vacuum cleaner, said portion of suctioned air and dust is introduced into the inside of the dust collecting unit through the collecting unit; a discharge unit for guiding so that air and the suctioned dust passing through the dust collecting unit are discharged into the transfer course of a flow of air generated by the suction force of the vacuum cleaner, and a foreign material discharge means for forcibly discharging dust stacked in the inside of the dust collecting unit into the outside by sliding-moving the dust collecting unit by an operation of a user and by communicating the vents with each other, wherein the dust collecting unit includes a first housing forming an outer appearance, and a second housing disposed vertically at the inside of the first housing, wherein the foreign material discharge means includes the first vent formed in the first housing and introducing outer air into the inside of the first housing, the second vent, formed in position different from the first vent, the second vent being formed in the second housing and selectively communicating with the first vent,an elastic member for selectively allowing air communication between the first vent and the second vent by elastically supporting the first housing or the second housing, and a push-button connected to the first housing or the second housing, wherein when an external pressure is applied to the push-button, the elastic member is compressed and the push-button and the first housing are moved downward to allow the first vent and the second vent to be positioned on a same line, thereby allowing the foreign material discharge means to force the air to flow into the dust collecting unit for forcibly discharging the stacked dust, wherein when the external pressure to the push-button is released, the push-button and the first housing are returned to their initial positions by the elastic member.