PURPOSE: To achieve a handy and highly accurate detection of position by detecting a conveying body optically during the movement, or during the movement and after the rest based on a specified optical pattern changing in the direction of a moving route.

CONSTITUTION: An optical pattern is composed of an area display pattern 21 on the black ground and a display pattern 22 for position in an area on a code plate 20. A band-shaped light flux emitted through a slit from a light source 30 is reflected at a specified part of an optical pattern existing near it to form an image 21' of an area display pattern cut out in a band from the optical pattern and an image 22' of a display pattern for position in an area on an image formation surface of a primary image sensor 40. The position of the optical pattern currently passing, namely, the position of a moving conveying body 10 is detected with a pattern processor.