PURPOSE: To measure the position of a hole readily, by providing a frame wherein pins that are to be inserted into reference holes of a material to be measured are provided, and making the distance between the reference pin and of an optical sensor that is provided at the frame equal to the distance between the reference hole of the material to be measured and a hole to be measured.

CONSTITUTION: A frame 10 has a triangle shape. Reference pins 14 and 16 are provided in the vicinities of both ends of a side 12 so as to pierce through the frame 10. The interval (y) between the reference pins 14 and 16 is equal to the distance between reference holes 20 and 22, which are provided in a material to be measured 18. An interval (x) between an optical sensor 24, which is provided at the lower surface of the frame 10 and the reference pin 14 is equal to the distance between the reference hole 20 of the material to be measured 18 and a hole to be measured 26. A digital computer 30 is connected to the optical sensor 24 through a lead wire 28. Deviations of the position of the hole to be measured 26 from the reference hole 20 or a specified position in the direction of X and Y can be displayed.