The present invention provides a bone fusion device which allows a distant bone body in a surgery direction to be pulled toward an adjacent bone body in the surgery direction while fusing the adjacent bone bodies. The bone fusion device includes a bone screw which includes a shank having an elongated shape with a circular cross-section, a screw thread formed on one end portion of the shank, and an adjustment female thread formed in the other end portion of the shank； a washer which includes a through hole into which the other end portion of the shank is inserted, and has a cross-sectional area larger than that of the bone screw； and an adjustment screw having an adjustment male thread screwed with the adjustment female thread of the bone screw through a through hole of the washer.
