The invention relates to a numerical-control double-cutter-head gear milling machine for straight bevel gears. The numerical-control double-cutter-head gear milling machine comprises a tool body assembly, a main driving box assembly, a cradle assembly, a cutting tool box assembly, a workpiece box assembly, a saddle turnplate assembly and the like. The numerical-control double-cutter-head gear milling machine is characterized in that the cutting tool box assembly comprises an upper tool holder component, a lower tool holder component, an upper tool box component, a lower tool box component, an upper-lower tool holder angle adjusting mechanism, an upper tool box transverse movement adjusting device and a lower tool box transverse movement adjusting device, and the upper tool holder component, the lower tool holder component, the upper tool box component, the lower tool box component, the upper-lower tool holder angle adjusting mechanism, the upper tool box transverse movement adjusting device and the lower tool box transverse movement adjusting device are installed on drum wheels of the cradle assembly. A spring damping device used for eliminating movement gaps during scale division actions is arranged in the workpiece box assembly. The numerical-control double-cutter-head gear milling machine has the advantages that the overall rigidity of a gear machine tool can be improved, the structure of the machine tool, various movement axis transmission chains and adjustment calculation programs are sufficiently simplified, the manufacturing cost is reduced, and the gear cutting machining accuracy is substantially improved; large-scale gear machining can be achieved, and requirements for machining a single gear or a small batch of various gears can be met.