A carbon membrane reactor as one of the applications of carbon membranes was newly developed and examined using dehydrogenation of cyclohexane as a test reaction. Permeation of hydrogen, argon, cyclohexane and benzene through carbon membranes showed the so-called molecular-sieving like diffusion behavior. The performance of the carbon membrane reactor for the dehydrogenation was found to exceed that of a normal reactor, i.e., equilibrium conversion.