PURPOSE: To automate measuring work or grinding work, by using three supporting legs, and making the profiling device to profile the surface of a work.

CONSTITUTION: One end of an expansion part 10, which is freely expanded and contracted in the direction of an arrow α which is intersected with a head part 1, is fixed to the tip of a robot arm or the head 1 of the main shaft of an NC machine tool. A moving part 30 is fixed to the tip of said expansion part 10. The moving part 30 is freely moved in the direction β and the direction γ that are intersected with the direction α and constituted so that both moving axes are intersected at a point 0. A three point supporting part 50, whose tips are contacted with three points A, B, and C on the surface of the object work, is attached to the part 0 of said moving part 30. A distance sensor, which measures the vertical distance from the surface of the object work along the central line passing a center G of a triangle plane formed by the points A, B, and C, is fixed to the head part 1.