A method for adjusting a load among subsystems in a communication network system having a bus network structure, wherein: the communication network system includes a broker processing a message routing, a connector, and a plurality of services which is a communicable terminal node connected to the broker via the connector, and the method includes the steps of: connecting all brokers of the communication network system to each other in a full mesh topology, the broker being a module setting up a routing path or a connection with the connector, to process the message routing; maintaining a broker list recording a network address of each broker in the connector; the connector receiving a service registration message from the service, randomly selecting one broker from the broker list, and transmitting a connection request message.