1. A moving object detection method comprising: acquiring at least two depth image frames including depth information, which are obtained by continuously taking images of a moving object, the at least two depth image frames including a present depth image frame and at least one past depth image frame; dividing each of the at least two depth image frames into a plurality of blocks; calculating differences between numbers of pixels positioned in respective different depth areas in each of the plurality of blocks in the present depth image frame, and numbers of pixels positioned in respective different depth areas in each of the corresponding plurality of blocks in each of the at least one past depth image frame, which correspond to the plurality of blocks in the present depth image frame; and detecting a moving block in the present depth image frame based on the calculated difference, and constituting the detected moving object, with the moving block.