A cable state monitoring device is simple in monitoring and sensitive in response, and belongs to the technical field of substation secondary equipment. The device comprises a detection device and a controller, wherein the detection device comprises a movable plate, a horizontal measurer, a balancing weight, a vertical rod, a first rotating bearing, a horizontal rod, a second rotating bearing, a flange ring and a shell; a detection device is arranged at the joint of the root of the primary equipment and the head end of the secondary cable; in the settlement process of the secondary cable to bemeasured, the flange ring pulls the horizontal rod; the horizontal rod drives the vertical rod to incline the movable plate; when the horizontal measurer is in a horizontal state, the mercury columnis located in the scale marks, when the horizontal measurer inclines, the mercury column moves in the inclination direction, then the conduction contact on the side face of the shell is communicated,the conduction contact generates pulses, the pulses are sent to the controller, and the controller receives the pulses and determines that the secondary cable sinks.