The real time observation of intramolecular vibrational energy redistribution has been carried out for the NH₂ symmetric and asymmetric stretching vibrations of jet-cooled aniline-d0 and aniline-d5. In both molecules, the IVR process can be described by two-step tier model. It was found that the isotope substitution affects the IVR rate oppositely between the symmetric and asymmetric vibrations. The observed results were compared with that of the OH stretching vibration of phenol, and it was concluded that out-of-plane vibrational modes play important roles as the doorway state in the IVR of the NH₂ stretches of aniline, while in-plane modes in phenol.