A lighting device, comprising: a casing having an inlet at one side for introduction of external air and an outlet at another side for discharge of the external air introduced through the inlet; a fan located within the casing to flow external air from the inlet to the outlet; an inlet cover that partially blocks an area of the inlet; and an air flow channel that communicates the inlet and the outside, wherein the air flow channel comprises: first and second contracting flow channels (210a, 210b) having a reducing sectional area advancing in an advancing direction of air; and first and second expanding flow channels (220a, 220b) that communicate with the contracting flow channels (210a, 210b) and that have an increasing sectional area advancing in an advancing direction of air, wherein in a connection portion between the first contracting flow channel and the first expanding flow channel, the advancing direction of air is changed; further comprising a floating matter collection portion confining matter introduced into the air flow channel, wherein the floating matter collection portion comprises: a first floating matter collection portion that communicates with the connection portion of the second contracting flow channel and the first expanding flow channel; a second floating matter collection portion that communicates with the first floating matter collection portion and located outwardly of the first floating matter collection portion; and a counterflow preventing piece extended from the inlet of the floating matter collection portion to the inside of the first floating matter collection portion. a casing having an inlet at one side for introduction of external air and an outlet at another side for discharge of the external air introduced through the inlet; a fan located within the casing to flow external air from the inlet to the outlet; an inlet cover that partially blocks an area of the inlet; and an air flow channel that communicates the inlet and the outside, wherein the air flow channel comprises: first and second contracting flow channels (210a, 210b) having a reducing sectional area advancing in an advancing direction of air; and first and second expanding flow channels (220a, 220b) that communicate with the contracting flow channels (210a, 210b) and that have an increasing sectional area advancing in an advancing direction of air, first and second contracting flow channels (210a, 210b) having a reducing sectional area advancing in an advancing direction of air; and first and second expanding flow channels (220a, 220b) that communicate with the contracting flow channels (210a, 210b) and that have an increasing sectional area advancing in an advancing direction of air, wherein in a connection portion between the first contracting flow channel and the first expanding flow channel, the advancing direction of air is changed; further comprising a floating matter collection portion confining matter introduced into the air flow channel, wherein the floating matter collection portion comprises: a first floating matter collection portion that communicates with the connection portion of the second contracting flow channel and the first expanding flow channel; a second floating matter collection portion that communicates with the first floating matter collection portion and located outwardly of the first floating matter collection portion; and a counterflow preventing piece extended from the inlet of the floating matter collection portion to the inside of the first floating matter collection portion. a first floating matter collection portion that communicates with the connection portion of the second contracting flow channel and the first expanding flow channel; a second floating matter collection portion that communicates with the first floating matter collection portion and located outwardly of the first floating matter collection portion; and a counterflow preventing piece extended from the inlet of the floating matter collection portion to the inside of the first floating matter collection portion.