An on-board warning apparatus of the invention includes an inattentive time measuring device that measures a duration of an inattentive state of a driver； a dozing time measuring device that measures a duration of a dozing state of the driver； a first warning output device that warns the driver when the measured inattentive time exceeds a first predetermined period of time Ta； and a second warning output device that warns the driver when the measured dozing time exceeds a second predetermined period of time Tb. The first predetermined time Ta is shorter than the second predetermined period of time Tb.
