A sequence-program design support device includes a display unit displaying a work screen corresponding to a designing work, an input unit receiving a setting operation of work phases, a zoom-in operation, and a zoom-out operation, a state storage unit storing the work phases and a current work, a work-model storage unit storing a partial order relation of a work specified for each of the work phases with a work screen corresponding to the work, and a control unit displaying a work screen corresponding to a next work of the current work in the order relation and storing the next work when the input unit receives the zoom-in operation with a first operation amount, and displaying a work screen corresponding to a previous work of the current work in the order relation and storing the previous work when the input unit receives the zoom-out operation with a second operation amount.