A continuous atmospheric horizontal dustfall flux measurement apparatus comprising: a dust sampling port that includes a ceiling plate, a side wall, and four or more partition plates; a suction pipe; a continuous dust amount measurement device that continuously measures a dust amount per unit time; a blower or a compressor; and an exhaust port, wherein a flow passage is formed by sequentially connecting the dust sampling port, the suction pipe, the continuous dust amount measurement device, the blower or the compressor, and the exhaust port so that suctioned air flows in series, wherein the side wall is a plate that has a vertical center axis and has a side surface with a substantially circular or polygonal truncated cone shape widened upward, wherein the side wall includes a suction port which is formed at a lower end thereof and is connected to the suction pipe and an external air inlet which has four or more openings disposed at a same interval in the circumferential direction of the side wall and at a same height near the upper end thereof, wherein the ceiling plate has a substantially disk shape, a diameter thereof is larger than a diameter of a horizontal cross-section of the upper end of the side wall, a center axis of the ceiling plate matches the center axis of the side wall, and the ceiling plate is connected to the upper end of the side wall so as to come into contact therewith, wherein the four or more partition plates are four or more flat plates which are disposed in a vertical plane so as to divide a space surrounded by the side wall into fan-shaped areas with a same size in a horizontal cross-section, are connected to each other on the center axis, and have a same height, and wherein the partition plates are connected to the side wall and to the ceiling plate without any gap therebetween. a dust sampling port that includes a ceiling plate, a side wall, and four or more partition plates; a suction pipe; a continuous dust amount measurement device that continuously measures a dust amount per unit time; a blower or a compressor; and an exhaust port, wherein a flow passage is formed by sequentially connecting the dust sampling port, the suction pipe, the continuous dust amount measurement device, the blower or the compressor, and the exhaust port so that suctioned air flows in series, wherein the side wall is a plate that has a vertical center axis and has a side surface with a substantially circular or polygonal truncated cone shape widened upward, wherein the side wall includes a suction port which is formed at a lower end thereof and is connected to the suction pipe and an external air inlet which has four or more openings disposed at a same interval in the circumferential direction of the side wall and at a same height near the upper end thereof, wherein the ceiling plate has a substantially disk shape, a diameter thereof is larger than a diameter of a horizontal cross-section of the upper end of the side wall, a center axis of the ceiling plate matches the center axis of the side wall, and the ceiling plate is connected to the upper end of the side wall so as to come into contact therewith, wherein the four or more partition plates are four or more flat plates which are disposed in a vertical plane so as to divide a space surrounded by the side wall into fan-shaped areas with a same size in a horizontal cross-section, are connected to each other on the center axis, and have a same height, and wherein the partition plates are connected to the side wall and to the ceiling plate without any gap therebetween.