Abstract: A dust-collecting device includes a cylindrical casing and an insertion part. The casing includes an introduction port introducing dust-containing air. The insertion part is positioned inside the casing to allow a swirling flow of the dust-containing air to be formed between the insertion part and the casing. The insertion part includes a cylindrical side surface part spaced away from and facing the casing and a projection part. The projection part includes, in a side of the first dust-collecting part, a projection surface projecting outward from the side surface part. The projection surface includes plural straightening parts and a connection part. The straightening parts are formed spirally toward the side of the first dust-collecting part, from upstream to downstream sides of the swirling flow. The connection part connects a downstream end side of one of the straightening parts and an upstream end side of another one of the straightening parts.

Abstract: A dust-collecting device includes a cylindrical casing and an insertion part. The casing includes an introduction port introducing dust-containing air. The insertion part is positioned inside the casing to allow a swirling flow of the dust-containing air to be formed between the insertion part and the casing. The insertion part includes a cylindrical side surface part spaced away from and facing the casing and a projection part. The projection part includes, in a side of the first dust-collecting part, a projection surface projecting outward from the side surface part. The projection surface includes plural straightening parts and a connection part. The straightening parts are formed spirally toward the side of the first dust-collecting part, from upstream to downstream sides of the swirling flow. The connection part connects a downstream end side of one of the straightening parts and an upstream end side of another one of the straightening parts.