Abstract: The present invention provides an adjustment device for adjusting the height of a washstand. The device utilizes a simple mechanism to allow a washstand, which fixed on a sliding beam, move up and down along a guiding track. The device also adjusts the height of the washstand as required by an actuating device. The adjustment device comprises a base, a sliding device, a sliding beam, and an actuating device. The sliding device is fixed on the base. The sliding beam connects to the sliding device in a way of moving up and down. The washstand is fixed on the sliding beam so that the washstand can move up and down. The actuating device provides necessary potential energy for lifting the washstand. Thereby the washstand fixed on the sliding beam can move up and down with the sliding device and the height, to which the washstand moves, is adjusted by the actuating device.