1. A robot apparatus which autonomously makes actions, based on external environment, comprising: image pick-up means for picking up an image of an object in the external environment; calculation means for calculating a circularity of a label included in image data based on the image picked up by the image pickup means; and distinguish means for distinguishing a characteristic part of the object, depending on the circularity calculated by the calculation means, wherein when the object is a toy having a rod-like bite part to be bitten and held by a mouth part formed in a head unit of the robot apparatus, and two side parts each formed in a substantially triangular shape and both formed respectively at two ends of the toy with the bite part interposed between the two side parts, circularities of labels based on a color applied to predetermined areas of the bite part and the two side parts are calculated by the calculation means, and the distinguish means distinguishes the bite part and the side parts from each other, based on the circularities.