Indoor semantic segmentation with RGBD input has received decent progress recently, but studies on instance-level objects in outdoor scenarios meet challenges due to the ambiguity in the acquired outdoor depth map. To tackle this problem, we proposed a residual regretting mechanism, incorporated into current flexible, general and solid instance segmentation framework Mask R-CNN in an end-to-end manner. Specifically, regretting cascade is designed to gradually refine and fully unearth useful information in depth maps, acting in a filtering and backup way. Additionally, embedded by a novel residual connection structure, the regretting module combines RGB and depth branches with pixel-level mask robustly. Extensive experiments on the challenging Cityscapes and KITTI dataset manifest the effectiveness of our residual regretting scheme for handling outdoor depth map. Our approach achieves state-of-the-art performance on RGBD instance segmentation, with 13.4% relative improvement over Mask R-CNN on Cityscapes by depth cue.