Evaluating car damages is crucial for the car insurance industry, but current deep learning networks fall short in accuracy due to inadequacies in handling car damage images and producing fine segmentation masks. This paper introduces MARS (Mask Attention Refinement with Sequential quadtree nodes) for instance segmentation of car damages. MARS employs self-attention mechanisms to capture global dependencies within sequential quadtree nodes and a quadtree transformer to recalibrate channel weights, resulting in highly accurate instance masks. Extensive experiments show that MARS significantly outperforms state-of-the-art methods like Mask R-CNN, PointRend, and Mask Transfiner on three popular benchmarks, achieving a +1.3 maskAP improvement with the R50-FPN backbone and +2.3 maskAP with the R101-FPN backbone on the Thai car-damage dataset. Demos are available at
https://github.com/kaopanboonyuen/MARS.