Acetylene black, activated carbon, and Ketjenblack were subjected to microwave heating up to 1000 °C under N2atmosphere to rapidly convert them into graphene-like materials. Few carbon materials exhibit a favorable increase in the intensity of the G’ band with increasing temperature. Upon electric field heating of acetylene black to 1000 °C, the observed relative intensity ratios of D and G bands (or G’ and G band) were equivalent to those of reduced graphene oxide heated under identical conditions. In addition, microwave irradiation under different conditions, i.e., electric field or magnetic field heating, produced graphene of qualities different from those of the same carbon material conventionally treated at the same temperature. We propose that this difference arises from the different mesoscale temperature gradients. The conversion of inexpensive acetylene black and Ketjenblack into graphene-like materials within 2 min of microwave heating is a major achievement toward low-cost mass synthesis of graphene.