Steam-methane reforming (SMR) is most commonly carried out in a catalytic reactor at temperatures from 700 to 1000 ℃. During the reforming reaction, the catalyst agglomerates under the high temperatures, showing degradation of catalytic performance with carbon deposition on the catalyst surface. Here, we report methane reforming in a steam plasma generated by microwaves at atmospheric pressure without the use of catalysts. The plasma reforming system is mainly composed of a 2.45 GHz microwave plasma torch and a plasma nozzle. Methane gas is introduced into the steam microwave plasma, which is stabilized by a swirl flow. The steam microwave plasma provides highly active species and a high-temperature plasma flame, enhancing the chemical reaction rate and eliminating the need for catalysts. We investigated the dependence of the hydrogen concentration on the steam to carbon ratio at a given plasma power. Using a specially designed plasma nozzle, we achieved high hydrogen concentrations (>70 vol.%) in the effluent streams.