PURPOSE: To measure the inner peripheral contour of a pipe by providing a main body having a hole extended along its central part, aligning means, coil attaching arm, eddy current coil, and biasing means which energizes one end of the arm and a coil assembly outward in the radial direction so that they can follow the inside diameter of the pipe.

CONSTITUTION: A cross-wound eddy current coil head 10 is attached to a driving mechanism 22 with a connector 24 and inserted into a pipe/sleeve 48 and 50 to be inspected. A wheel 28 aligns the head 10 being moved in the axial direction while the wheel 28 is rotated by the mechanism 22 so as to make the rotation of the head 10 smoother. Since the head 10 is moved in the axial direction in a rotating state, the eddy current coil assembly 18 of the head 10 scans the inner peripheral surfaces of the pipe/sleeve 48 and 50 along a spiral route. While the assembly 18 scans the inner peripheral surfaces, a counter magnet 46 energizes one end of a coil attaching arm 16 and assembly 18 outward in the radial direction so that they can closely follow the inner peripheral surfaces of the pipe/sleeve 48 and 50. The head 10 generates signals through the assembly 18 while the head 10 is rotated and an electronic device receives and processes the signals.