A user interface device is provided that includes a hardware interface connectable to different types of external devices and an internal control device configured to perform a single control process to implement one of functions that corresponds to at least one of a type of an external device connected to the hardware interface or whether an external device is connected to the hardware interface. The internal control device executes, from among tasks constituting the single control process, a task that corresponds to timing of inputting a press manipulation using an input switch, blinks the light-emitter at a predetermined speed while the task is in execution, and steadily lights the light-emitter when terminating the task and prompting the user to input a next press manipulation.