This invention relates to a method of measuring the shape of an object in a non-contacting manner. The method comprises the steps of providing reference points on the object, the coordinates of which are known in an object coordinate system for expressing the shape of the object; applying a light spot on the reference points while moving a light spot detecting sensor to determine the coordinate values in a measuring coordinate system; determining the relative positional relation between the two coordinate systems by using coordinate values thus determined and the coordinate values in the object coordinate system; measuring points on the object to measure the shape of the object; and comparing the coordinate values, relating to shape of the object and determined in the measuring coordinate system, with reference values which are design values modulated with the relative positional value and converted into coordinate values in the measuring coordinate system in an arithmetic control unit, whereby a manufacturing error of said object is measured.