The present invention relates to a process and to a device for manufacturing synthetic gas. The reactor in accordance with the invention comprises within a single housing: a non catalytic combustion chamber (1) comprising at least one fuel injection element (2) and at least one oxidizer injection element (3) so as to achieve a partial combustion in said chamber referred to as "sufficient residence time chamber", and at least one catalytic bed (4) into which the gases coming from combustion chamber (1) run, and further comprising at least one additional oxidizer injection element (6) and at least one fuel injection element (7). The reactor and the process in accordance with the invention may be applied to any chemical manufacturing utilizing synthetic gas.