In the transurethral lithotripsy using flexible endoscope (f-TUL), a flexible ureteroscope is inserted into the bladder from the urethra and breaks calculus by laser transmitted through an optical fiber. Because laser irradiation position is fixed in the endoscopic field of view, it is difficult to perform precise alignment of laser to the target when the target has relatively complex structure. To solve the problem, a thin multidirectional active bending mechanism of the laser fiber using Shape Memory Alloy (SMA) wire has been developed. This device has 170 µm diameter channel for laser fiber and is controlled by 3 SMA wires. Maximum outer diameter is 1.1 mm and length of the bending part is 10 mm. The fabricated bending mechanism with laser fiber bends up to 10 degrees. Surface temperature was measured by using a thermocouple in water bath and was lower than 41°C.