A data sharing system includes communicable terminals and selects a server-client system in which a first terminal is designated as a server and other terminals are designated as clients, when a sum of estimated time for transferring data to the first terminal from the other terminals, estimated time for performing, by the first terminal, arithmetic processing of the data in the first terminal, and estimated time for transferring arithmetically processed data from the first terminal to the other terminals satisfies a real time restriction, and power estimated to be consumed at a time of performing, by the first terminal, the arithmetic processing of the data in the first terminal is less than power estimated to be consumed at a time of performing the arithmetic processing by the other terminals. The data sharing system selects a peer-to-peer system, when the sum does not satisfy the real time restriction in any terminal.