1. A method of switching an application server, for controlling to take over a first task provided by a first application server to a second application server, the method being executed by a management computer coupled to the first application server for providing the first task and the second application server for providing the second task, the method including: a first step of referring, by the management computer, to switching level information including switching patterns to be used at a time of switching the first task to the second application server, and setting a level of a degree of safety for each of the switching patterns; a second step of referring, by the management computer, to the switching level information, and setting a switching time for the each of the switching patterns, which is required for switching the first task to the second application server; a third step of referring, by the management computer, to task requirement information including a stop time for each first task which is allowed at the time of switching the first task to the second application server; a fourth step of comparing, by the management computer, the stop time included in the referred task requirement information which is set to the first task and the switching time which is set to the each of the switching patterns included in the referred switching level information, and selecting one of the switching patterns having a switching time that is shorter than the stop time of the task requirement information which is set to the first task and having the level of the degree of safety that is highest among the switching patterns of the switching level information; and a fifth step of stopping, by the management computer, the second task of the second application server by the selected one of the switching patterns, and then controlling the second application server to provide the first task.