A road friction coefficient detecting apparatus and method of a vehicle includes a vehicle data calculating section, a tire characteristic initial value judging section and a road friction coefficient estimating section. In the vehicle data calculating section, parameters needed for the calculation of road friction coefficients are established based on signals from a steering wheel rotation angle sensor, a vehicle speed sensor and a yaw rate sensor. The tire characteristic initial value judging section sends a signal to establish parameters corresponding to a low friction coefficients to the vehicle data calculating section, when road condition sensing means such as an outside air temperature, a rain fall sensor and the like detect a road surface having a relatively low friction coefficient. When the road condition sensing means detect a road surface having a relatively high friction coefficient, the tire characteristic initial value judging section sends a signal to establish parameters corresponding to a friction coefficient immediately before the previous stop of the vehicle. In the road friction coefficient estimating section a road friction coefficient is calculated based on these parameters according to the adaptive control theory.