The diagnostic technique of the rf glow discharge at 13.56 MHz is developed by using the spatiotemporally resolved optical emission spectroscopy. New experimental evidence that the temporal excitation rate at the sheath peaks in phase with the maximum of the total current is obtained in a parallel‐plate geometry at 13.56 MHz in CH4(10%)/H2under a typical condition of the plasma chemical vapor deposition of amorphous carbon film at room temperature.