A dust collecting device comprising: a whirl formation unit arranged in a blow passage for air containing dust and configured to form a whirl; and a dust collection chamber configured to collect and store dust separated by the whirl formation unit, wherein the whirl formation unit includes a tubular casing including an air inflow port arranged at an upstream side of air flowing through the blow passage, an air outflow port arranged at a downstream side of the air flowing through the blow passage, and a dust discharge port arranged in a circumferential portion connected to an opening of the dust collection chamber, the dust collecting device characterized in that: the whirl formation unit further includes a spiral swirl enhancement surface formed around a center axis extending through a center of the tubular casing and arranged at an upstream side of the air flowing through the blow passage in the tubular casing, wherein the spiral swirl enhancement surface extends toward a downstream side of the air flowing through the blow passage so that an opening between an initial end and a terminal end of the spiral swirl enhancement surface serves as the inflow port; the inflow port includes two sides lying along the initial end and the terminal end of the spiral swirl enhancement surface and another side lying along a portion of a side wall of the tubular casing; and planes of the inflow port and the discharge port each have a parallel relationship with an axial direction of the center axis. a whirl formation unit arranged in a blow passage for air containing dust and configured to form a whirl; and a dust collection chamber configured to collect and store dust separated by the whirl formation unit, wherein the whirl formation unit includes a tubular casing including an air inflow port arranged at an upstream side of air flowing through the blow passage, an air outflow port arranged at a downstream side of the air flowing through the blow passage, and a dust discharge port arranged in a circumferential portion connected to an opening of the dust collection chamber, the dust collecting device characterized in that: the whirl formation unit further includes a spiral swirl enhancement surface formed around a center axis extending through a center of the tubular casing and arranged at an upstream side of the air flowing through the blow passage in the tubular casing, wherein the spiral swirl enhancement surface extends toward a downstream side of the air flowing through the blow passage so that an opening between an initial end and a terminal end of the spiral swirl enhancement surface serves as the inflow port; the inflow port includes two sides lying along the initial end and the terminal end of the spiral swirl enhancement surface and another side lying along a portion of a side wall of the tubular casing; and planes of the inflow port and the discharge port each have a parallel relationship with an axial direction of the center axis. the whirl formation unit further includes a spiral swirl enhancement surface formed around a center axis extending through a center of the tubular casing and arranged at an upstream side of the air flowing through the blow passage in the tubular casing, wherein the spiral swirl enhancement surface extends toward a downstream side of the air flowing through the blow passage so that an opening between an initial end and a terminal end of the spiral swirl enhancement surface serves as the inflow port; the inflow port includes two sides lying along the initial end and the terminal end of the spiral swirl enhancement surface and another side lying along a portion of a side wall of the tubular casing; and planes of the inflow port and the discharge port each have a parallel relationship with an axial direction of the center axis.