Disclosed are herein an apparatus and method for extreme ultraviolet (EUV) spectroscope calibration. The apparatus for EUV spectroscope calibration includes an EUV generating module, an Al filter, a diffraction grating, a CCD camera, a spectrum conversion module, and a control module that compares a wavelength value corresponding to a maximum peak among peaks of the spectrum depending on the order of the EUV light converted from the spectrum conversion module with a predetermined reference wavelength value depending on an order of high-order harmonics to calculate a difference value with the closest reference wavelength value, and controls the spectrum depending on the order of the EUV light converted from the spectrum conversion module to be moved in a direction of wavelength axis by the calculated difference value. Thus, it is possible to accurately measure a wavelength of a spectrum of EUV light used in EUV exposure technology and mask inspection technology.