This paper proposes and evaluates a new task scheduling method for parallel and distributed applications in an environment consisting of multiple networks having different characteristics. The proposed method can schedule both streaming applications and non-streaming applications effectively at the same time, since it selects the most suitable networks for the communications of tasks and considers the changing loads of the networks. The experimental results show the proposed method reduced the total execution time of a practical streaming application. The dispersion of the execution time was also suppressed even if the network bandwidth was dynamically changing. This characteristic is very important when this method is applied to more complicated task scheduling methods.