A simple and unified heuristic method for nicely drawing directed, undirected and mixed graphs is proposed basing upon a new model called magnetic-spring model which is an extension of Eades's spring model. In the new model, the idea of controlling edge orientations by magnetic forces is employed. Since the method is conceptually intuitive, it is quite easy to understand, implement, tune and improve it. Examples of layouts and results of experiments are shown to demonstrate extensive possibilities of the method.