1. An article recognition apparatus comprising: a marker having four or more unit pattern marks which are provided at a predetermined positional relationship on an article to be recognized and which are formed in such a way that a density pattern sequentially changes from a center position to a periphery of each of the four or more unit pattern marks; an imaging tool that is disposed opposite the article to be recognized and that captures an image of the marker; a supporting mechanism that physically supports the imaging tool so as to enable setting of the imaging tool at least at a non-face-up measurement position where an imaging plane of the imaging tool does not directly face up a surface of the marker provided on the article to be recognized and in a view field range of the imaging tool; and a layout information recognition block that recognizes layout information about a position and an attitude of the article to be recognized by use of at least imaging information about the marker whose image has been captured by the imaging tool placed at the non-face-up measurement position, wherein the supporting mechanism moves the imaging tool to a first measurement position at which the marker provided on the article to be recognized enters the view field range of the imaging tool and is measured such that an overhead view of the marker may be captured and to a second measurement position made up of the non-face-up measurement position at which the marker enters the view field range of the imaging tool and at which measurement is performed at a higher degree of accuracy than at the first measurement position.