Welding apparatus and welding method

A welding method, comprising:

• controlling a position and a posture of a shape sensor with respect to an object to be welded, based on position and posture data;
• extracting shape data representing an outline of the object to be welded, from measured data measured by the shape sensor whose position and posture are controlled based on the position and posture data;
• calculating coordinate transformation data for correcting the shape data, based on the position and posture data;
• correcting the shape data using the coordinate transformation data;
• extracting a plurality of points of change in shape, from the corrected shape data;
• extracting a plurality of points of change in shape corresponding to end portions of a bead, from the corrected shape data;
• calculating a width of the bead and an inclination angle of a groove surface, based on the corrected shape data and the plurality of points of change in shape;
• determining welding conditions, and a position of the welding torch and a posture of the welding torch with respect to the inclination angle of the groove surface, based on the width of the bead;
• and
• performing welding based on the welding conditions, and the position and the posture of the welding torch.