The utility model discloses a dehumidifying device used in a fully-sealed control cubicle. The cabinet comprises a cabinet body bottom plate, a ventilation hole is formed in the middle of the cabinetbody bottom plate, and a guide rail, a heater and a long-stroke electric cylinder are arranged on the upper surface of the cabinet body bottom plate; a sliding block used in cooperation with the guiderail is installed on the guide rail, the top of the sliding block is connected with a supporting plate, a push rod of the long-stroke electric cylinder is connected with the side face of the slidingblock through a push rod connecting piece, and the supporting plate and the sliding block are driven by the long-stroke electric cylinder to move horizontally along the guide rail. A short-stroke electric cylinder located above the supporting plate and an axial fan located below the supporting plate are arranged on the supporting plate, and a push rod of the short-stroke electric cylinder penetrates through the supporting plate and then is connected with a sealing gasket located below the supporting plate; and a ventilation assembly is arranged above the axial fan. According to the utility model, the gas in the cabinet cavity is dehumidified in a heating and exhausting combined manner, and the vent hole of the control cubicle can be sealed after the dehumidification is finished.