To simplify a structure by shortening the wiring of vibration sensors, confirming the closing of a window by an alarm device, and detecting and alarming abnormal vibration by the right and left vibration sensors.

In this locking device for the window locking left and right window frames 1, 2 by a crescent lock 4 installed at the mating part 3 of these both window frames 1, 2, the vibration sensors 7, 8 detecting the vibration of window panes 5, 6 are stuck on the window panes 5, 6 near the crescent lock 4. The alarm device 10 is installed in proximity to the crescent lock 4. When both window frames 1, 2 are set at the same closing positions, one terminal 12 of the vibration sensor 7 is continued with the alarm device 10. Since a crescent lever 11 is rotated to the closing position, the other terminal 13 is continued with the alarm device 10 to bring both vibration sensors 7, 8 in an alarm operation state.