A counterweight mounting device, which is installed on a frame supporting a counterweight, includes a first link of which a lower end is coupled to the frame so that the first link is rotatable about a first hinge shaft, a second link including a slot guide into which a second hinge shaft coupled to an upper end of the first link is inserted and in which the second hinge shaft slides, a hydraulic cylinder of which a lower end is coupled to the frame so that the hydraulic cylinder is rotatable about a cylinder rotation shaft and an upper end is coupled to the second hinge shaft and rotates the first link, and a connection member installed on an upper end of the second link and connected to the counterweight.