Document management system

[Problem] To ensure security in document management in small-scale organizations without using expensive servers by establishing peer-to-peer connection of a plurality of PCs, and to enable mutual non-tampering certification among connected organizations.[Solution] Provided is a document management system in which is formed a PC group in which a plurality of small electronic computers for creating, recording, and viewing a document are connected via a communication channel, said system comprising i) an in-PC cluster document synchronization means which causes a document recorded on one PC to be incorporated in recordings of other PCs belonging to a cluster, (ii) a document hash value generation means which generates a hash value of the document, and (iii) a blockchain generation means which assembles a plurality of the generated hash values and forms a block, connects the block to the existing blocks and forms a blockchain, and synchronizes and records same on the PCs within the PC cluster.