Speeding up of parallel computation is to be achieved. A parallel computation method comprises a step for distributing respective first-level small pieces of data, that are formed by dividing data, to respective computation nodes in plural computation nodes; a step for further dividing, in at least one first computation node in the plural computation nodes, the first-level small piece of data into second-level small pieces of data; a step for transferring, in parallel, the respective second-level small pieces of data from the at least one first computation node to the plural computation nodes; a step for transferring, in parallel, the transferred second-level small pieces of data from the respective computation nodes in the plural computation nodes to at least one second computation node in the plural computation nodes; and a step for reconstructing, in the at least one second computation node, the first-level small piece of data by using the second-level small pieces of data transferred from the plural computation nodes.