The carrier cooling and the carrier relaxation of an InN thin film illuminated with two excitation energies of 1.53 and 3.06eV were studied by an ultrafast time-resolved photoluminescence upconversion apparatus. The hot phonon effect could be accounted for longer effective phonon emission times as compared to the theoretical prediction. The rise time and the LO phonon emission time for 3.06eV excitation were much smaller than those for 1.53eV excitation. These differences were attributed to the intervalley scattering between the Γ 1 and Γ 3 valleys in InN when carriers were excited with the energy of 3.06eV. The intervalley scattering times of 250fs and 2ps were estimated for the intervalley scattering from the Γ 1 to Γ 3 valley and the reversed scattering process, respectively.