1. A traffic monitoring device, which comprises: an object information acquiring section including a detection block calculating unit for acquiring, with the use of distance images acquired by imaging an object from above within a supervised sector that is divided into a plurality of blocks, a block having distance measured pixels, obtained by imaging the object from above, as a detection block related to an object present within the supervised sector and operable to acquire a three dimensional object information by the detection block; a block projected image generating unit for generating a two dimensional image, which is a height data of the detection block, by projecting onto a horizontal plane the detection blocks, each having a height data on a two dimensional plane: a template setting unit for setting a template block of a shape related to an object with a block area containing a head, a hairdos buffer unit and a shoulder rendered to be a template image; a template matching unit for performing a template matching with the block projected image by means of the template block; and a determining unit for determining the number of objects based on the template matching.