A lighting device includes a casing having an inlet that introduces external air at one side and an outlet that discharges the introduced air at the other side. A fan is located within the casing to flow external air from an inlet direction to an outlet direction. An inlet cover blocks at least an upper area of the inlet to prevent external air from being directly introduced into the inlet. An air flow channel communicates the inlet and the outside, and includes two contracting flow channels having a reducing sectional area in an advancing direction of air. The two expanding flow channels communicate with the contracting flow channels and have an increasing sectional area in an advancing direction of air, so that in a connection portion of the contracting flow channel and the expanding flow channel, the advancing direction of air is changed.