Thawing is achieved by applying high-frequency power to a frozen material (R) sandwiched between opposing electrodes. A thawing section of a thawing apparatus (10) includes unit electrodes (302) for a first electrode group as a former stage, unit electrodes (303) for a second electrode group as a latter stage, and unit electrodes (304) for a third electrode group as a further stage. The unit electrodes (302) for the first electrode group are set so that the area of the electrode surface is smaller than the area of the sandwiched surface of the frozen material (R). The unit electrodes (303) for the second top electrode group are larger than the area of the unit electrodes (302) for the first electrode group. The unit electrodes (304) for the third electrode group are larger than the area of the unit electrodes (303) for the second electrode group.