PURPOSE: To measure the robot data showing a misregistration amt. with high accuracy and efficiently by providing an arithmetic means calculating the robot data on the slippage of the positional coordinate of the body to be detected and the original positional coordinate by input data based on the output detecting signal of the detector detecting the relative positional coordinates to one face of the body to be detected.

CONSTITUTION: The body 31 to be detected is of hexahedronal shape and moved with the movable part of a robot 30. On the other hand, a positioning plate 33 is fixed to a preset relative position to the robot 30. A detector 34 is fixed to the optional hole of the porous part 32 of this positioning plate 33, opposed by being separated to one face of the body 31 to be detected and detects the relative positional coordinate to one face of the body 31 to be detected. Then, an arithmetic means 35 calculates the robot data concerning the slippage of the positional coordinate of the body to be detected and the original positional coordinate by the input data based on the output detection signal of this detector 34.