To analyze the movement of a human body at high speed by means of a simple circuit configuration, to measure a stay time and to output a detection result by constituting a sensor with a picture sensing processor where picture detecting and processing circuits are contained in one chip, arithmetic IC, a dip switch for setting a human body critical stay time, and a circuit for outputting an abnormality signal to an external part, etc.

When a locus sensor is arranged on the ceiling of a toilet, for example, and a person enters the toilet and stays at a human body detecting area, only the person moving in a picture is detected by a picture detecting and processing IC 9, the movement of the person is replaced with coordinates X and Y by an arithmetic IC 10 and the stay time in the same coordinates is measured. When the stay time exceeds the time which set by a dip switch 14 of the arithmetic IC 10, a signal is outputted from an output circuit 11. Besides, the locus of the person in the human body detecting area is outputted from the output circuit 11 to an external part in coordinates X and Y in serial communication with a mode changeover.