Disclosed herein is a load balancing method and apparatus which can efficiently distribute load to a plurality of servers providing a software streaming service where a bandwidth-on-demand is different depending on sending times, and a software streaming system using the same. Sessions established between the servers and clients are classified into first sessions which send data for initial execution and second sessions which send data desired by users after the initial execution is completed, and the resulting session information of each of the servers is collected. A total load amount of each of the servers is calculated under the condition that different load weights are applied to the first and second sessions. A server with a minimum one of the total load amounts is selected from among the servers by comparing the total load amounts of the servers with one another, and the selected server is allocated to a new client requesting the software streaming service.