A height-adjustable spinal fusion cage including a first end plate and a second end plate, a distal movement block fixed to be relatively movable to a dove-tail groove formed at a distal end of each of the first end plate and the second end plate; a proximal movement block fixed to be relatively movable to a dove-tail groove formed at a proximal end of each of the first end plate and the second end plate, an adjusting member rotatably fixed to the proximal movement block and screw-coupled to the distal movement block to adjust a distance between the distal movement block and the proximal movement block, and a vertical guide portion formed to be disposed at the first end plate and the second end plate and provide support for a load in a longitudinal direction or width direction of the first end plate and the second end plate.