We present a plan for calibration of the NeXT hard X-ray telescopes (HXT) at the synchrotron radiation facility, SPring-8. In hard X-rays, it is difficult for a laboratory-based beamline using a conventional X-ray source to provide sufficient capabilities for pre-flight high-precision calibration. Therefore, we plan to characterize the NeXT HXT at the SPring-8 beamline BL20B2. SPring-8 is one of the world's third-generation synchrotron radiation facilities. Measurements at BL20B2 have great advantages over those done with conventional sources, such as an extremely high flux, a larger beam with less divergence, and a selectable, narrow bandwidth covering the hard X-ray region from 8 to over 100 keV. The 16m-long experimental hutch has sufficient capability for characterization of the NeXT HXT (FL=12m). In the past, we have measured the Point Spread Function (PSF) and effective area of telescopes for balloon-borne hard X-ray imaging experiments (e.g. InFOCuS, SUMIT) at several energies from 20 to 60 keV. Furthermore, we have successfully established a tuning procedure to improve their image quality. We plan to measure the X-ray characteristics (PSF, effective area, stray light, and so on) of the NeXT HXT to build up the HXT response function.