Conventionally, when executing a plurality of programs while being synchronized by a plurality of debuggers, an interface has been required for performing a particular coordination between the debuggers. In the present invention, programs are synchronously executed without coordination between the debuggers by performing a control method including a step for maintaining a program execution state in the debuggers to be different from an actual program execution state, so that the program execution is retained, if necessary, in response to a program execution request from a debugger.