A network load balancing system which includes a client that sends data, a plurality of servers, each capable of performing data processing, which receives the data, and a third control unit which transfers the data sent by the client to one of the servers, the third control unit comprising:
- a conversion information storing unit to store conversion information which represents a correspondence relationship of the client to each of the servers;
- a distributive relay unit to transfer the data sent by a first server to one or more of the servers according to the correspondence relationship in the conversion information stored in the conversion information storing unit;
- a distribution ratio adjusting unit to adjust the correspondence relationship in the conversion information stored in the conversion information storing unit;
- and
- a load measuring unit to measure a load on each of the servers and to notify the distribution ratio adjusting unit of load conditions of the servers in order to allow the distribution ratio adjusting unit to adjust the correspondence relationship in the conversion information stored in the conversion information storing unit.