A form measuring mechanism (100) which measures form of an object (102) by bringing a probe (124) into direct contact with the object includes a plurality of reference spheres (130a, 130b) for calibrating the probe, a judging system/controller (154) for judging form abnormal values common in position and size to each other and form abnormal values not common to each other obtained by measuring the reference spheres, and a notifying display unit (156) for notifying at least any one of a contamination or dust adhering state of the probe judged from the common form abnormal values and a worn state and contamination or dust adhering states of the reference spheres judged from the form abnormal values not common to each other. Accordingly, it becomes possible to identify contamination or dust adhesion of the probe or contamination or deformation due to wearing of a reference sphere, and at least in the case of contamination or dust adhesion of the probe or reference sphere, the location of the contamination or dust adhesion can be identified, and in the case of wearing of the probe or reference sphere, a situation of the worn region can be identified or necessity of replacement of the probe or reference sphere can be judged.