PURPOSE: To accurately and inexpensively measure the shape of a platy body having an indefinite shape by supporting the platy body with an arm the end section of which opposite to its free end section is fitted to a machine base in a state where the platy body can be freely tilted against a supporting member and providing a surface detector at the part of the free end section of the arm which is brought into contact with a part to be measured.

CONSTITUTION: A supporting member 1 is mounted on a machine base and an arm 2 is fitted to the member 1 by means of hinges 3 so that the arm 2 can be freely tilted against the member 1. At the left end of the arm 2, a projection 2b is provided to hang a tension spring 8 and a long hole 2c is provided to pass a guide bolt 7. When a platy member 10 is pushed, the right upper corner of the member 10 collides with the lower surface 2a of the arm 2 and pushes the arm 2 upward. Since the corner then collides with the projection 4e of a detecting lever 4 and pushes the section 4e upward, a microswitch 6 generates a signal. As a result, the position of the right upper corner of the member 10 can be recognized and the right-side profile of the member 10 can be discriminated. When the member 10 further advances and the left upper corner of the member 10 passes under the projection 4e of the lever 4, the switch 6 is turned off and the left-side profile of the member 10 can be discriminated.