Cutting method and cutting apparatus

A cutting apparatus for cutting a steel sheet, comprising:

• at least one robot having an arm capable of changing a position and a posture of the arm;
• a nibbler that has a cylindrical case, a punch housed inside the case, which reciprocates in a top-bottom direction to punch the steel sheet, and a die provided below the case, and that is mounted on a tip of the arm of the robot;
• a guide member provided in the vicinity the die of the nibbler located at a cutting position along a moving path of the nibbler;
• and
• a controller that controls the robot to move the nibbler along the guide member, wherein
• the guide member has a first guide surface for restricting movement of the nibbler from the cutting position to a first side of a direction perpendicular to a traveling direction of the nibbler and the top-bottom direction by contact with a side surface of the die of the nibbler located at the cutting position.