PURPOSE: To provide the plant monitoring method and device which can make monitoring operation easy and efficient.

CONSTITUTION: Plant facilities are photographed by an ITV camera 30 and a three-dimensional image of the same scene with an ITV image is generated from the photography data and the arrangement design data base 32 of the plant facilities; and an abnormal position in the three-dimensional image is highlighted with the signal of a sensor which detects abnormality and its abnormal position image is superimposed on the ITV image. Consequently, the state of the circumferential site of the abnormal position can be grasped and the monitoring operation is made easy and efficient.