1. A near-surface object sensing device, comprising a printed circuit board; a plurality of magnetic sensors arrayed on the printed circuit board to sense magnetic field of an external magnetic object and generate a plurality of magnetic sensing signals; a multiplexer electrically connected to the magnetic sensors for selecting at least one of the magnetic sensing signals to be output; and a microprocessor electrically connected to the multiplexer for receiving the at least one of magnetic sensing signals, wherein the microprocessor comprises: a sampling algorithm module for converting the at least one of magnetic sensing signals into a magnetic field distribution image having north-polarity parts and south-polarity parts, and a six-dimensional coordinates-calculating module for calculating six-dimensional coordinates of the external magnetic object.