To provide a data communication method for data facilities, preventing the intercept of communication data from the outside.

In the data communication method for transmitting/receiving data among a prize management POS 3, a ball counter 4, a ball dispenser 5, an automatic vending machine 6, equipment 7 in game facilities including a game machine and a hall computer 2 for managing the equipment in the game facilities, each of the equipment 7 in the game facilities and the hall computer 2 stores an open key pkx for encoding data transmitted to owned equipment, a secret key skx for decoding encoded data transmitted to the owned equipment and an open key pkx for encoding data transmitted to all other equipment than the owned equipment. When transmitting the data to other equipment than the owned equipment, the equipment 7 in the game facilities and the hall computer 2 transmit the encoded data using the open key pkx for the corresponding equipment, and the corresponding equipment receiving the encoded data decodes the encoded data using the secret key skx stored in the equipment.