Abstract: A metal object detection system comprising a matrix sensor having sensing units arranged like a matrix and a signal processing system for driving the matrix sensor for detecting a metal object. The signal processing system comprises circuitry for driving the matrix sensor and inputting a reception signal from the sensor, a plurality of peripheral detection points surrounding a main detection point, and circuitry which, when a metal object detection response is made at the main detection point by a sensing unit contained in the monitor frame, compares the response with a response of each of other peripheral detection points in the frame. When, the response of the main detection point is the largest, the circuitry determines that a metal object exists at the main detection point.