In a plasma reactor for decomposing a hydrocarbon fluid, the deposition of C particles is to be reduced or completely prevented. In order to achieve this object, there is described a plasma reactor for decomposing a hydrocarbon fluid which comprises a reactor chamber enclosed by a reactor wall and having at least one hydrocarbon fluid inlet and at least one outlet, and in addition it comprises a plasma burner having at least two elongated electrodes which each have a base part that is fixed to the reactor wall and a burner part which projects into the reactor chamber and has a free end. The hydrocarbon fluid inlet opens out into the reactor chamber in such a manner that a hydrocarbon fluid flowing out therefrom flows in a space between the reactor wall and the electrodes along at least one electrode to the free end thereof. A high flow rate of the fluid is thereby achieved and the direction of flow of the incoming fluid is directed away from the hydrocarbon fluid inlet.