An embodiment of a data transmission method is executed by a server that includes a memory that stores first unique number data presenting a first unique number and second unique number data presenting a second unique number, in association with each other, and includes receiving a first unique number data presenting a first unique number from a first electronic device in the first unique number reception step. Whether the first unique number presented by the first unique number data received in the first unique number reception step matches the first unique number presented by the first unique number data stored in the memory is determined in the determination step. The second unique number data stored in association with the first unique number data stored in the memory is transmitted to the first electronic device when determined in the determination step that they match.