We applied a femtosecond transient reflecting grating (TRG) method to solid/liquid interfaces to successfully observe the photoinduced ultrafast relaxation dynamics at TiO2(001)/KSCN (aq) interfaces, We found, for the first. time, an ultrafast relaxation component (110-690 fs). The component intensity clearly increases with increasing concentration of KSCN, and it is strongly dependent on the number of photoexcited carriers, We concluded that this component is due to the interaction between photoinduced nonequilibrium holes and adsorbed SCN-ions and that ultrafast charge transfer occurs by way of this interaction. These results suggest a new ultrafast charge transfer process involving nonequilibrium carriers.