Depth edges play an important role in depth image upsampling. Many recent upsampling methods rely on the prior images of depth edges to preserve sharp depth edges in restored depth images. However, recent depth edge detection methods are not robust against the noise in depth images. Some methods are also too time-consuming. We propose a method to efficiently detect edges in depth images. The proposed method is very simple but very robust against the noise in depth images. It is also fast and has near δ(1) implementation. We apply the proposed method to the existing edge guided depth image upsampling. Experimental results on both simulated and real data show the effeδctiveness of the proposed method.