PURPOSE: To minimize the ringing of the radar so that the radar can accurately detect a buried object by providing a mechanism which can change the distance between ground surface or water surface and a reception antenna.

CONSTITUTION: A transmission and reception antennas 3 and 5 are arranged on an antenna elevating/lowering device 12. An oscillator 2 generates a high-frequency pulse synchronously with a signal from a timing circuit 1 and impresses the pulse upon the transmission antenna 3. The high-frequency pulse is radiated into the ground as electromagnetic waves. When the antennas 3 and 5 do not match the ground surface 10, ringing is generated due to multiple reflection and the detecting accuracy drops. A matching detection circuit 11 finds and records the sum of absolute values of ringing. The circuit 11 repeats the finding and recording operations at each position over the antenna height adjusting width H of the device 12 and designates the antenna height at which the ringing becomes the minimum to the device 12. A sampler 7 samples the data of reflected waves from a buried object 4 at the designated antenna height and sends the data to a display device 8. By repeating these operations at a plurality of points on the ground surface 10, the picture of the object 4 is displayed on the device 8.