To acquire information of food relating to a cash register and a microwave oven by one time operation of a bar code reader, control the information by the cash register, transmit heating information of food necessary to be heated, and heat the food by the microwave oven.

The information on the food 1 is acquired by the bar code reader 4 of the cash resister 3 from a bar code 2 of the food 1. The food 1 is classified into the food 1 necessary to be heated and the food 1 unnecessary to be heated by the cash register 3 from the information. Process is completed only by the cash register 3 for the food 1 unnecessary to be heated. In the case of the food 1 necessary to be heated, the heating information of the food 1 is transmitted to the microwave oven 5 from the cash resister 3 by a transmitting cable 10 or the like, and the food 1 is heated by the microwave oven 5 in accordance with the heating information.