For a notchback model, the time-averaged wake pattern basically consists of the arch vortex behind the rear window and the trailing vortices behind the trunk deck. However, the unsteady characteristics of these wake patterns have not been clarified yet. In this study, we attempted to analyze the unsteady wake structure using flow visualization and measuring velocity fluctuation. As a result, it was found that the critical geometries which increase the aerodynamic drag have the L-type vortex behind the rear window. The L-type vortices intermittently occur at the right-side or left-side rear window and are swept out. (The time-averaged pattern of the L-type vortices is similar to the arch vortex.) It was clarified that the L-type vortex is related to the aerodynamic drag.