1. An image recognition device comprising: an imaging means for capturing an object to be measured on a floor mat and a three-dimensional reference in one image; a three-dimensional measurement reference provided on the floor mat so that it is within a predetermined range from the object to be measured and including more than or equal to four points placed at predetermined positions relative to the imaging means; and an image position calculation means for extracting an image corresponding to the object to be measured and the three-dimensional measurement reference from the captured image and calculates a position of the object to be measured on the basis of a position information of the three-dimensional measurement reference that is previously obtained and stored and a distortion information relating to distortion of the image of the three-dimensional measurement reference captured by the imaging means.