The present disclosure relates to an apparatus and a method for detecting a radar mounting angle. The present disclosure provides an apparatus for detecting the radar mounting angle that includes a controller configured to determine a vehicle driving state of the vehicle, select a moving target when the vehicle driving state of the vehicle is determined to be straight driving, store a position of the moving target and generate a moving target driving lane of the moving target based on position information on the moving target, and detect a radar mounting angle of the vehicle using the generated moving target driving lane of the moving target.