A method of creating, by a computer, a task plan that prescribes an execution time of a task on which a completion time limit is set, the method includes allocating the execution time of at least one first task in a first period, calculating a first total time length for execution of the at least one first task allocated in the first period, identifying at least one second task that is not allocated in the first period and has the completion time limit set in the first period, calculating a second total time length for execution of the at least one second task, and displaying the first total time length and the second total time length on a display device.