A roller hemming device capable of correcting a positional error between a robot manipulator and a workpiece, and carrying out a pre-hemming and/or hemming process with appropriate pressing force. The roller hemming device has a position detecting part adapted to detect a current position of a roller attached to a front end of the robot manipulator; a force sensor arranged between a wrist section of the robot manipulator and the roller; and a controller adapted to control the position of the roller by using an output of the position detecting part and an output of the force sensor, so that pressing force applied to a mold by the roller is a predetermined value.