A three-dimensional shaping method that includes lamination comprising alternately repeating a powder layer forming step and a sintering step in which the powder layer is sintered by irradiation of a moving laser beam or electron beam, wherein the following process is adopted during the sintering step: a. measuring the reflection intensity of the laser beam or electron beam irradiated during each sintering step, or irradiation of light other than the laser beam on the whole sintering region, and measuring the reflection intensity of that light, in each sintering step, b. commanding to continue sintering in the next time unit or the next powder layer forming step, when, in a time unit within the time necessary for each sintering step, it has been detected that the reflection intensity of the process a is within a standard range for reflection intensity in which no sintering defects are produced, c. commanding to cancel sintering in the next time unit or the next powder layer forming step under a judging that a sintering defect has occurred, when, in a time unit within the time necessary for each sintering step, it has been detected that the reflection intensity of the process a has deviated from the standard range for reflection intensity in which no sintering defects are produced, the method characterized by d. taking spectral images for the laser beam or electron beam, or reflected light other than the laser beam that has been reflected from the sintering region where the sintering defect has occurred causing commanding in the process c, and from the sintering region within the subsequent time unit, based on the intensity corresponding to each wavelength according to a spectral function, e. judging that the cause of the sintering defect that resulted in commanding in the process c is a problem with the control system related to the laser beam or electron beam, when each spectral image in the process d is unchanged or changes only gradually, and judging that the cause of the sintering defect is a problem with the powder layer-formed surface, when each spectral image in the process d changes rapidly. a. measuring the reflection intensity of the laser beam or electron beam irradiated during each sintering step, or irradiation of light other than the laser beam on the whole sintering region, and measuring the reflection intensity of that light, in each sintering step, b. commanding to continue sintering in the next time unit or the next powder layer forming step, when, in a time unit within the time necessary for each sintering step, it has been detected that the reflection intensity of the process a is within a standard range for reflection intensity in which no sintering defects are produced, c. commanding to cancel sintering in the next time unit or the next powder layer forming step under a judging that a sintering defect has occurred, when, in a time unit within the time necessary for each sintering step, it has been detected that the reflection intensity of the process a has deviated from the standard range for reflection intensity in which no sintering defects are produced, the method characterized by d. taking spectral images for the laser beam or electron beam, or reflected light other than the laser beam that has been reflected from the sintering region where the sintering defect has occurred causing commanding in the process c, and from the sintering region within the subsequent time unit, based on the intensity corresponding to each wavelength according to a spectral function, e. judging that the cause of the sintering defect that resulted in commanding in the process c is a problem with the control system related to the laser beam or electron beam, when each spectral image in the process d is unchanged or changes only gradually, and