Maze procedure has achieved high cure rates and become the surgical golden standard for the treatment of atrial fibrillation. But, atrial arrhythmia after maze procedure is often persistent and drug-resistant. In these cases, diagnosis by electrophysiological study (EPS) and treatment by catheter ablation (ABL) are useful. In our hospital, maze procedure has been actively performed for mitral valve surgery with atrial arrhythmia. We examined the cases that required ABL after maze procedure in our hospital. We reported 2 such typical cases where ablation of cavo-tricuspid isthmus line (CTI) in the right atrium and left superior pulmonary vein-left atrial appendage space( LSPV-LAA ridge) in the left atrium was effective.