The electrochemical cell consisting of a gadolinium-doped ceria porous electrolyte (GDC, Ce_0.9Gd_0.1O_1.95), Ni (20 and 30 vol %)–GDC bilayer cathode and Ru (20 and 30 vol %)–GDC bilayer anode was used for the dry-reforming of a real biogas with CO₂ or air using pulsed current (0.1, 1, 10, 100 Hz) under the applied voltage of 0.5 V. The composition of the supplied gas was adjusted to CH₄/CO₂ = 1/1 volume ratio in the dry-reforming with CO₂ at 800°C (CH₄+ CO₂ → 2H₂ + 2CO). The conversion ratios of the supplied CH₄ and CO₂ were 60.8–80.6 and 71.8–85.9%, respectively. The outlet gas contained 8.9–29.6 vol % H₂ gas. The increase in the frequency of the pulsed current decreased the formation rates of H₂ and CO gases. Carbon was deposited on the cathode by the disproportionation reaction of CO gas and the thermal decomposition of CH₄. When air was mixed with the biogas, stable reforming to produce H₂ and CO gases proceeded for 24 h at 700–800°C using pulsed current. The formation rates of H₂ and CO gases were independent of the frequency of the pulsed current. The oxygen gas of air reacted with the carbon deposited on the cathode and removed it as CO gas.