A privileged node holds a secret key (SKEY), and normal nodes each hold a public key (PKEY). The normal nodes each include a transaction inputting unit that receives transaction data (TDATA), a transaction transmitting unit that transmits the TDATA, a transaction managing unit that manages a transaction history in a form of blockchain, and a block receiving unit that receives blocks from the privileged node. The privileged node includes a transaction receiving unit that receives TDATA from each of the normal nodes, a block generating unit that generates a signature value (SIG) on the basis of a SKEY, and generates a block containing TDATA and the SIG, and a block transmitting unit that transmits blocks. The transaction managing unit adds a block to the blockchain on condition that the authenticity of the SIG in the block is confirmed by using the PKEY.