A lamination molding apparatus is provided capable of preventing damage to a cutting device. Every time a sintered body including a sintered layer group consisting of a predetermined number of sintered layers is formed, gas is injected from a gas injector toward a vicinity of a side surface of the newly formed sintered body so as to blow off material powder, and then the side surface of the sintered body is shaved by a cutting tool of the cutting device, wherein the gas injector blows off the material powder by only intermittent injection which repeats short-time gas injection or by a combination of the intermittent injection and continuous injection which continuously injects the gas.