An on-board warning device according to an embodiment of the present invention is provided with: a first processing unit that executes first face detection processing on each item of image data input at a predetermined frame rate; a second processing unit that executes second face detection processing on the image data, the second face detection processing being different from the first face detection processing; a warning output unit that issues a warning; and a state discrimination unit that switches face detection processing to be executed on the input image data from the first face detection processing by the first processing unit to the second face detection processing by the second processing unit when a predetermined condition is satisfied and that controls the warning output unit to issue the warning when the state of a person as detected from the input image data as a result of the second face detection processing is an inattentive state.
ON-BOARD WARNING DEVICE