To completely bore an air vent in the sealing material of even a completely sealed food and to prevent the taste of the food from being impaired due to that its smell is soaked into other foods by providing a boring device in the machine and boring the air vent by a boring instrument which is always new.

A minor carriage device 11 on which a container 1 is placed moves to below the boring device 12 first and the boring device 12 bores an air vent in the sealing material which seals a food. Then the minor carriage device 11 moves to below a heating device 13, which heats the food in the container. The heating device 13 moves down from above to container 1 when the minor carriage device 11 moves to below the heating device 13 and stops, thereby heating the food in the container. After the heating, the minor carriage device 11 moves to below a food lifting device 14 and stops. Consequently, the air vent can easily be bored in the sealing material and this machine is sanitarily preferable.