The invention discloses a detection device capable of adjusting a single area and double areas and a detection method thereof. The detection device comprises a material conveyor belt and a material detector, wherein the material conveyor belt comprises a first conveyor belt and a second conveyor belt, and the material detector comprises a first detection piece and a second detection piece. The first detection piece comprises a first detection head A and a first detection head B correspondingly arranged on the two opposite sides of the first conveyor belt, and the second detection piece comprises a second detection head X and a second detection head Y correspondingly arranged on the two opposite sides of the second conveyor belt. The detection device further comprises a horizontal moving unit for driving the first detection head B and the second detection head Y to move horizontally. According to the detection device capable of adjusting the single area and the double areas, by arranging the first detection head B and the second detection head Y on the horizontal moving unit, the positions of the first detection head B and the second detection head Y can be adjusted according to thedemands so that detection of the single area and the double areas can be adjusted according to the demands, and the application range is wide.