A mixing device for a fuel reformer for mixing at least two fluids is provided. The mixing device includes at least a first plurality of holes which is arranged along a first row, and a second plurality of holes which is arranged along a second row. The mixing device can be used in a fuel reformer for converting hydrocarbon fuel into hydrogen rich gas by auto-thermal reaction process having a, preferably cylindrically shaped and double walled, housing with two side walls forming a reaction chamber of the fuel reformer, wherein hydrocarbon fuel and an oxidizing agent are mixed by the mixing device.