Disclosed is a top-fill humidifier easy to wash and without water leakage. The humidifier comprises a single-piece body having a hollow chamber with a wall and bottom; and an isolator removably assembled in the chamber to divide the chamber into a storage sub-chamber between the isolator and the wall of the chamber and a vaporizing sub-chamber between the isolator and the bottom of the chamber. In such a humidifier, the isolator divides the chamber in the body into a storage chamber and a vaporizing chamber, which may solve the problem of water leakage and facilitate the washing of the humidifier.