The invention provides an output torque control method and apparatus for a lean burn internal combustion engine which accounts for aging of component parts, and in which no stepwise change of torque or shock occur when an air fuel ratio is changed. The method and apparatus according to the invention control an intake air amount while maintaining an emission purification function by controlling the air fuel ratio to that of a theoretical mixture (air fuel ratio of 14.7) in a case where a limit NOx emission is determined by using a detected air fuel ratio and lean burn operation becomes difficult due to the amount of NOx emissions. Abrupt change of an output torque when the air fuel ratio is changed is curtailed by controlling a fuel amount or an air amount after calculating the fuel amount or the air amount from an engine speed and an accelerator depression angle.