A laser welding nozzle used as a working tool, a linear movement mechanism of a pressing device, and a servomotor are fixed to a bracket. A roller support frame is fixed on a moving side of the linear movement mechanism. A roller is pivotally mounted at a distal end of the roller support frame. The roller is located in the vicinity of a weld point of the laser welding nozzle. By driving the servomotor in a controlled manner, a portion in the vicinity of the weld point of a plate portion to be welded is pressed by the roller to restrain a floating of the weld portion, by which a gap between the plate portions is regulated, and thus uniform weld can be obtained. The pressing position, speed, and pressing force of roller can be controlled easily, so that the pressing device can be used for various types of workpieces.