1. A person counting device comprising: a single panorama image generator configured to match a plurality of images respectively captured by a plurality of cameras and generate a single panorama image; a line inserter configured to insert an imaginary line to the single panorama image; and a person counter configured to allocate identification numbers to respective persons in the plurality of images and count the number of persons that pass the imaginary line, wherein the person counter comprises: an image restorer configured to restore the single panorama image including the imaginary line to a plurality of images including same imaginary line information and determine the number of persons that pass a new imaginary line in each of the plurality of restored images, wherein each of the new imaginary line inserted in each of the plurality of the restored images is derived from the same imaginary line information; and a duplication remover configured to rule out a number of duplicate-counted persons by using the identification numbers allocated to the respective persons in the plurality of images and imaginary line information.