In an automatic operation system including: a positioning robot having a holding tool and an inertial sensor at a tip end portion of an arm thereof; a working robot having an operation tool at a tip end portion of an arm thereof; and a robot control device, a positioning correcting method of the present invention includes: conveying and positioning the holding tool, which holds a work, by the positioning robot at a positioning reference position of the holding tool corresponding to an operation position of the work; detecting a displacement amount of the holding tool from the positioning reference position by the robot control device based on an inertial force of the inertial sensor when the working robot carries out a predetermined operation with respect to the work; and correcting based on the detected displacement amount the positioning reference position of the holding tool to a position of the holding tool before the holding tool is displaced.