Micro-machining of a brittle material such as glass or silicon is important in micro fabrication. Particularly, micro-abrasive jet machining ($mu$-AJM) has become a useful technique for micro-machining of such materials. The $mu$-AJM process is mainly based on the erosion of a mask which protects brittle substrate against high velocity of micro-particles. Therefore, fabrication of an adequate mask is very important. Generally, for the fabrication of a mask in the $mu$-AJM process, a photomask based on the semi-conductor fabrication process was used. In this research a rapid mask fabrication technology has been developed for the $mu$-AJM. By scanning the focused UV laser beam, a micro-mask pattern was fabricated directly without photolithography process and photomask. Therefore, rapid and economic mask fabrication can be possible for the micro-abrasive jet machining. Two kinds of mask patterns were fabricated by using SU-8 and photopolymer (Watershed 11110). Using fabricated mask patterns, abrasive-jet machining of Si wafer was conducted successfully.