A vehicle accessory adjusting system that adjusts a variety of on-vehicle accessories of a vehicle to suit a driver or a passenger according to personal data stored in an IC card or other portable data storage medium. The vehicle accessory adjusting system includes a memory that stores standard setting data on the on-vehicle accessories, calculation circuit for calculating personal data based on specific setting data obtained when a driver or a passenger uses some on-vehicle accessories and corresponding standard setting data of the on-vehicle accessories, a rewriting unit to rewrite the personal data stored in the IC card with new personal data; and setting circuit to set the on-vehicle accessories according to the personal data stored in the IC card and the standard setting data stored in the memory.