Abstract: A user interface designing apparatus capable of easily designing a user interface which can change over display parts in accompanying state transitions for events by adding/deleting states and editing the display part and event handling in each state. The apparatus includes a state set editing means for adding/deleting states of a composite display part having a plurality of states, an event handling editing means for describing an event handling for state transition in each state of the composite display part, an elementary display part storing means for storing elementary display parts designed previously, and a state display editing means for adding/deleting elementary display parts to be displayed in each state of the composite display part.