A program preparation system includes: a display unit displaying a first task input section to which a content of a first task to be executed by a target device is inputted and a second task input section to which a content of a second task to be executed by the target device is inputted, the second task being different from the first task; an intermediate code generation unit generating an intermediate code, using information inputted to the first task input section and information inputted to the second task input section; and a program conversion unit converting the intermediate code into a multitasking program causing the target device to execute the first task and the second task.