A monitoring device for preventing urinary incontinence has the following components: a high-frequency constant-current power supply adapted to supply a pair of terminals which are set on the surface of a human body across the urinary bladder; a high-frequency voltage signal detecting means which conducts wave detection from a high-frequency voltage signal sensed by a pair of sensing electrodes which are set on the human body surface at positions on the path of the high-frequency electrical current flowing between the pair of terminals; a DC component detecting means 13 which detects the DC component of the signal detected by the high-frequency voltage signal detecting means; a variance component detecting means for detecting variance component of the signal detected by the high-frequency voltage signal detecting means; a variance-to-DC ratio computing means for computing the ratio between the DC component and the variance component; and a variance-to-DC ratio evaluating means for activating an informing means when the computed value of the variance-to-DC ratio has reached a predetermined threshold level.