Abstract: There is provided a secret data transmission method where a first device generates plural pieces of distributed data including data of a master key and transmits these by wireless communication to a second device and where the second device receives the plural pieces of distributed data and reconstructs the master key, wherein the first device arranges data obtained by performing an EXOR operation in sequence on plural pieces of random number data and the master key to generate secret data, generates a last piece of distributed data by performing an EXOR operation in sequence on the plural pieces of distributed data and the secret data, and transmits the plural pieces of distributed data to the second device, and the second device performs an EXOR operation in sequence on the plural pieces of distributed data to reconstruct the secret data, divides the reconstructed secret data, and performs an EXOR operation on the divided pieces of data to reconstruct the master key.