A seatbelt fastening prompting apparatus comprises a display device of driving assistance information which displays driving assistance information on a screen, a seatbelt fastening detection device which detects a fastening situation of a seatbelt as to whether the seatbelt is fastened or unfastened, a vehicle speed detection device which detects a vehicle speed, and a control device which allows the screen to display warning contents to the effect that the seatbelt should be fastened, when an ignition switch is turned on and the seatbelt is detected as being unfastened by the seatbelt fastening detection device. In the seatbelt fastening prompting apparatus, the warning contents are changed to raise a warning level thereof step by step in accordance with the vehicle speed.