PURPOSE: To highly accurately transfer information group to a substrate at low cost by a structure wherein a positioning mechanism consists of a centering member, which abuts against the inner wall of the center hole of the substrate at positions such as three points equidistant from the center axis of a base member and at the same time the radial distance between the abutting part of which and said center axis is variable, and an adjusting means to adjust the radial distance.

CONSTITUTION: A centering member 31 consisting of three abutting parts 28, 29 and 30 is provided on a guide member 26, which is fixed to a supporting member 23 by a screws 27. The respective abutting parts are arranged equidistant from the center axis of a shaft 22 so as to be able to abut against the inner wall of a center hole formed on a substrate 15. The radial distances between the respective abutting parts 28, 29 and 30 and the center axis of the shaft 22 are variable. An adjusting means to adjust the radial distances between the respective abutting parts and the center axis of the shaft 22 consists of a moving member 38, an O-ring 39, a screw 41, an intermediate member 42, coiled springs 43 and 29, a piston 46 and peripheral members.