A robot controller, by which an operator can visually or intuitively understand the direction and/or magnitude of an actual force applied to an arbitrary portion of a workpiece. The controller controls a motion of a robot so that one of a work tool and a workpiece is moved relative to the other, and carries out a predetermined operation. The controller has a force detecting part which detects a force acting between the work tool and the workpiece; and a displaying part which displays a simulated image or video of the robot. The displaying part displays a trajectory of working points on the workpiece, and the force detecting part detects the force applied to each working point when the work tool passes through the working point. The displaying part displays the detected force as a line segment, etc., extending from the working point or a point near the working point.