Abstract: A dehumidifier may include a main body, a heat exchange unit inside the main body, and a water tank on the water tank chamber or separated from the water tank chamber through a side surface of the main body. The water tank may store condensed water generated in the heat exchange unit. A movable member may be inside the water tank to vertically move according to a water level of the condensed water stored in the water tank. One or plurality of first sensors mounted on a wall defining the water tank chamber may detect the movable member. A second sensor mounted on a position of the wall, which is higher than the first sensors may detect the movable member. A control unit may receive the detected results of the first and second sensors to control an operation of the heat exchange unit or an occurrence of an alarm signal according to the received results.