The invention relates to the technical field of monolithic roadbed disassembly, and discloses an ejecting device for disassembling monolithic roadbeds. The ejecting device comprises an ejecting main plate; a push rod and a movable rod are mounted in an outer cylinder; a pressure spring is mounted between the push rod and the movable rod; a sealing plate is movably inserted in a rotating drum; a sand outlet is formed in the top of the rotating drum; the sealing plate is provided with a through hole corresponding to the sand outlet; a sand box is fixedly connected to the top of the rotating drum; fine sand is placed in the sand box; and sand holes corresponding to the sand outlet are formed in the top and the bottom of the outer cylinder. The ejecting main plate is placed between main sections and disassembly sections of the monolithic roadbeds; and through design of traditional single-section hydraulic rod structures as push rod and movable rod two-section structures, the preferable butting of the disassembly sections by each movable rod is effectively guaranteed, so that the condition of nonuniform stress of the disassembly sections due to incapability of hydraulic rods effectivelybutting against the disassembly sections caused by uneven sections of the disassembly sections is prevented, and smooth disassembly work is guaranteed.