Ultrafast carrier relaxation in AlαGa1-αAs/GaAs multiple quantum wells is studied using femtosecond absorption saturation measurements with an excited photon energy higher than that of the band gap of the barrier layers. Carriers generated in the well layers and in the barrier layers scatter out of the excited states to a quasi-equilibrium state in 30 and 130 fs, respectively. Carrier capturing from the barriers to the wells occurs mainly during the carrier cooling and recombination in the time scale of picoseconds.