A hair dryer includes a main body, a handle, and a diffuser. The diffuser includes a diffusing case having a rear side coupled to the main body. The main body is provided such that a front end of an outer wall surrounds a gas or air outlet, and a first coupling portion coupled with the diffuser is provided at the front end. The diffusing case includes a second coupling portion coupled to the first coupling portion while surrounding a gas or air inlet hole defined at the rear side. The first coupling portion includes a power transmitter to supply power to the diffuser, and the second coupling portion includes a power receiver to receive the power from the power transmitter.