The present invention provides a tray for frozen food enabling frozen food such as frozen sushi on the tray to be suitably thawed and to provide a frozen food package or a frozen sushi package using this tray, and a method of thawing frozen sushi in this package. The tray for frozen food 1 comprises a base 3, concavities 2 caved in the base 3, a surrounding wall 4 standing from the periphery of the base 3, a flange 5 composing the top end of the surrounding wall 4, a downward flap 6 extending downwardly from the outer peripheral edge of the flange 5, an overhanging portion 7 overhanging outward from the lower edge of the downward flap 6, ribs 8 formed at corners between the base 3 and the surrounding wall 4, and bulges 9 standing from the base 3. The tray 1 is composed of a body 1a made of a synthetic resin and a dielectric material layer 1b formed on the outer surface of the body 1a. Frozen sushi 10 is disposed such that the shari ball 11 is entirely or mostly positioned within the concavity 2 and the neta 12 is entirely positioned above the level of the base 3. The frozen sushi is thawed in such a manner that the shari ball 11 is thawed with heat transmitted from the dielectric material layer 1b by heating the frozen food package by a microwave oven and the neta 12 is thawed with heat transmitted from the shari ball 11 after stopping heating the package in the microwave oven.