The needs of automated inspection system are grown for the flat panel displays (FPD). However, it is so difficult to detect the defects on the surface of FPD due to non-uniform intensity distribution through the whole panel. Especially, curve-type defects such as micro sized thread and scratch are too difficult to detect with the conventional methods. In this paper, we propose a robust detection algorithm for curve-type defects. The proposed algorithm is composed of flattening, segmentation, and classification. The flattening makes intensity distribution likely to be uniform. The segmentation extracts candidates of curve-type defect and the classification selects real defects from candidates. The experimental result verifies the performance of the proposed method.