A hair dryer includes a main body and an outlet unit. The outlet unit is provided therein with an air-guiding member, which can convert a linearly ongoing air current into a rotationally ongoing air current. Furthermore, the outlet define a plurality of air holes, through which outside air can be drawn into the outlet unit to mix with the air current flowing out of the exit of the main body, to increase air speed, uniformity and penetration and to reduce noise.