Charge and lattice dynamics has been investigated for Na_0.79Co[Fe(CN)₆]_0.902.9H₂O film at 300 K by means of the time-resolved x-ray diffraction apparatus coupled with the in situ time-resolved absorption measurement. We observed an uniform lattice expansion whose relaxation time is ∼ 40 ns. Based on the close correlation between the charge and lattice dynamics, the lattice expansion is ascribed to the photo-created charge-transferred Co²⁺ - Fe³⁺ state.