A humidifier for which the cleaning of a water tank is easy includes: a water tank which is mounted inside a housing and stores water; a humidification member which is immersed in the water stored in the water tank and performs humidification; a water container provided with an opening/closing valve which is opened and closed to supply water stored therein to the water tank; a water container support member which is detachably mounted to an upper part of the water tank and on which the water container is seated; and a water supply control member which is mounted to the water container support member and opens and closes the opening/closing valve so that the water can be supplied from the water container to the water tank.