The present invention relates to a laser safety device. By combining: a transesophageal probe comprising a transesophageal light receiving portion for receiving laser light and proximal light output portion for emitting at least a part of the received light； an optoelectronic converting unit for producing an electric signal indicative of an amount of the light emitted from the proximal light output portion； an analyzing unit for processing the electric signal and for comparing the processed electric signal with a set point criterion； and a control unit for controlling a laser on the basis of the comparison in the analyzing unit, it is possible to detect laser light that has been emitted in the left atrial wall and has been transmitted into the esophagus, in order to avoid overheating of mediastinal structures.
