A laser processing machine , comprising: a laser oscillator configured to generate and emit a laser beam; a processing head configured to irradiate a sheet metal (W) with the laser beam emitted from the laser oscillator to cut the sheet metal (W); an assist gas supply device configured to supply an assist gas to the processing head so as to blow the assist gas onto the sheet metal (W); a NC device configured to control the laser oscillator ; and a reflected beam detector configured to detect a reflected beam reflected from the sheet metal (W) when the sheet metal (W) is irradiated with the laser beam to cut the sheet metal (W); characterized in that the laser processing machine further comprises: a standard deviation value calculation unit configured to calculate, in a predetermined calculation cycle, a standard deviation value of a reflected beam detection value at a monitoring wavelength from among reflected beam detection values in a predetermined wavelength band output from the reflected beam detector ; and a quality determination unit configured to determine whether or not a burning defect has occurred in which a cut surface of the sheet metal (W) is excessively melted based on a comparison result of comparing, with a first threshold value, the standard deviation value calculated by the standard deviation value calculation unit . a laser oscillator configured to generate and emit a laser beam; a processing head configured to irradiate a sheet metal (W) with the laser beam emitted from the laser oscillator to cut the sheet metal (W); an assist gas supply device configured to supply an assist gas to the processing head so as to blow the assist gas onto the sheet metal (W); a NC device configured to control the laser oscillator ; and a reflected beam detector configured to detect a reflected beam reflected from the sheet metal (W) when the sheet metal (W) is irradiated with the laser beam to cut the sheet metal (W); characterized in that the laser processing machine further comprises: a standard deviation value calculation unit configured to calculate, in a predetermined calculation cycle, a standard deviation value of a reflected beam detection value at a monitoring wavelength from among reflected beam detection values in a predetermined wavelength band output from the reflected beam detector ; and a quality determination unit configured to determine whether or not a burning defect has occurred in which a cut surface of the sheet metal (W) is excessively melted based on a comparison result of comparing, with a first threshold value, the standard deviation value calculated by the standard deviation value calculation unit . a standard deviation value calculation unit configured to calculate, in a predetermined calculation cycle, a standard deviation value of a reflected beam detection value at a monitoring wavelength from among reflected beam detection values in a predetermined wavelength band output from the reflected beam detector ; and a quality determination unit configured to determine whether or not a burning defect has occurred in which a cut surface of the sheet metal (W) is excessively melted based on a comparison result of comparing, with a first threshold value, the standard deviation value calculated by the standard deviation value calculation unit . <EOS>