PURPOSE: To quickly cope with even a line forming a curve by recognizing the direction of the line from the floor surface picture picked up by a television camera to move it along the recognized line.

CONSTITUTION: The floor surface picture is picked up by the television camera which is mounted on a carrier and looks down at a certain angle. An edge extracting part 1 extracts positive and negative edges of the line by first-order differentiation in the vertical direction of the picture. A noise eliminating part 2 eliminates the noise in the picture. An edge width calculating part 3 counts the number of picture elements from the positive edge to the negative edge in each scanning line to calculate the distance between positive and negative edges. A line inclination calculating part 4 calculates a ratio of the essential width of the line to the distance between positive and negative edges in each scanning line obtained by the edge width calculating part 3 to calculate the inclination of the line. It is judged by the change of positions of positive and negative edges before and after the scanning line that the line has a right-hand or lef-hand inclination.