Carbon nanoplates with diameters and thicknesses of up to approximately 1.2 μm and 18 nm, respectively, were prepared by a reaction using CaC2, ferrocene, and NH4HCO3 as starting materials at 600 °C for 10 h. These carbon nanoplates form aggregates that have a specific surface area of up to 831 m2 g–1 and a specific capacitance of up to 184 F g–1 at a scanning rate of 10 mV s–1 in a 3 mol L–1 H2SO4 solution. Without using NH4HCO3, hexagonal carbon nanoplates with an average edge length of 500 nm and thickness of approximately 22 nm were obtained with a specific capacitance of up to 42 F g–1. If NaN3 or NaHCO3 was used instead of NH4HCO3, carbon nanoplates with a curved surface or irregular circular carbon nanoplates were obtained with specific capacitances of 87 or 36 F g–1, respectively.