A lamination molding apparatus includes a chamber that covers a molding region, an irradiator that irradiates a material layer formed in the molding region with a laser beam or an electron beam and forms a solidified layer, a supply port that supplies an inert gas to the chamber, a discharge port that discharges the inert gas from the chamber, an inert gas supplier which is connected to the supply port and supplies the inert gas to the chamber, a fume collector, and an oxygen concentration adjustor. The fume collector has an inlet, a charging section, a collecting section, and an outlet. The oxygen concentration adjustor is connected between the discharge port and the charging section and supplies, to the fume collector, an adjusting gas having an oxygen concentration higher than an oxygen concentration of the inert gas which is discharged from the discharge port.