1. A person counting device comprising at least one processor to implement: 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; a person counter configured to allocate identification numbers to respective persons in the single panorama image and count the number of persons that pass the imaginary line; 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 a plurality of images which are restored from the single panorama image, information regarding overlapping regions between the plurality of images, and imaginary line information, wherein the person counter, in the restored plurality of images, allocates a same identification number to a person in the overlapping regions between the plurality of images.