Provided is a position controller for a flexible substrate (100) provided in a processing apparatus conveying a band-shaped flexible substrate (1) in a longitudinal position, in the lateral direction and processing the substrate in a processing unit (20) installed on a conveying path of the substrate. The position controller for the flexible substrate includes a pair of sandwiching rollers (131 and 132) that sandwiches an upper edge of the substrate; a supporting mechanism (140) that supports the pair of sandwiching rollers so as to be rotatable and movable close to or away from each other; an urging device (150) that applies a pressing force to the pair of sandwiching rollers through the supporting mechanism; and a pressing force adjusting device (160) adjusting the pressing force from the urging device, wherein each roller constituting the pair of sandwiching rollers is a conical roller having a circumferential surface inclined with respect to the axial direction, and is supported to the supporting mechanism so that a small diameter side of each conical roller is located at a center side of the substrate in the lateral direction and the rotation direction of a sandwiching surface of the substrate is the same as the conveying direction of the substrate.