A computer system includes a plurality of computer nodes, each including an external communications unit. An application unit executes processing in accordance with a processing request. A synchronization unit establishes synchronization of the processing between each computer node and other computer nodes. The processing is executed by each computer node, and an inter-node communications unit executes transmission/reception of information between each computer node and the other computer nodes. The synchronization unit transmits the processing request to the other computer nodes via the inter-node communications unit, the processing request being received by the external communications unit. Also, the synchronization unit receives processing requests from the other computer nodes as well via the inter-node communications unit. Based on the number of the computer nodes that have received the same processing request via the external communications units, the synchronization unit selects a processing request that should be executed by the application unit.