Road surface condition determination apparatus

A comparison/determination part 7 recieves the input of a front wheel speed filtered value omega fF from a front wheel speed filtered value calculation part 5 and a rear wheel speed filtered value omega rF from a rear wheel speed filtered value calculation part 6. It is determined whether the front wheel speed filtered value omega fF has exceeded a preset first threshold C1. It is determined whether the rear wheel speed filtered value omega rF has exceeded a preset second threshold C2 within a time for transmission of vibration from the front wheels to the rear wheels which is experimentally set in advance after the front wheel speed filtered value omega fF exceeded the first threshold C1. The road surface is then determined to be rough when it is determined that the rear wheel speed filtered value omega rF has exceeded the preset second threshold C2.