This study investigated on the characteristics of flow-induced vibrations of two circular cylinders in staggered arrangement. The response characteristics on elastically supported two circular cylinders were examined by a free vibration test. Measurements were performed for stagger angle α=5°, 10°, 15°, 25°, 45°and 60°, and the spacing between two cylinders L/D=0.1-3.2, where α is the angle between the free-stream flow and the line connecting the centers of two cylinders, L is the gap width between two cylinders, and D is the diameter of two cylinders. The new findings for characteristics of flow-induced vibrations of two cylinders in staggered arrangement are as follows. (i) There were seven patterns of flow-induced vibration with changing stagger angle a and spacing ratio L/D, (ii) the generation mechanism of flow-induced vibration was clarified by doing flow visualization test and generation regions of flow-induced vibration at each stagger angle were arranged, (iii) when the cylinder was perturbed at stagger angle 10 and 15 degrees, flow-induced vibration genetated two cylinders was a divergent vibration, (iv) there were two patterns of flow-induced vibration at critical spacing L/D in which exist two flow patterns.