A microwavable vacuum-packed frozen sushi product comprising: a flexible microwave-safe plastic packing bag which is vacuumed to a pressure of 50 to 600 mmHg and, in the pressure-reduced state, hermetically sealed; an open-topped plastic box placed in said packing bag; and a sushi product placed in said box; said vacuum-packed frozen sushi product being such that a space is formed in said packing bag in the pressure-reduced state around said sushi product and the space has, in total, a volume 0.1 to 0.7 times that of said sushi product; an inner surface of said packing bag is in contact with an upper surface of said sushi product; and said packing bag, said box and said sushi product are frozen together in a unified form. Water vapor generated during thawing is allowed to flow through a space formed between the sushi material and the box and the packing bag to heat a rice section and a material or materials, thereby providing the sushi product with diminished unevenness in temperature distribution.