Abstract: An automatic pin inserting apparatus for inserting a pin into a frame-shaped workpiece, in particular, a frame-shaped workpiece having a welded structure. The apparatus includes a table freely movable in X and Y directions, and moving means for moving the table in these directions, which correspond to right-and-left directions as well as up-and-down directions. An optical detecting means is provided for detecting a hole location in each workpiece placed on the table, as is a swing arm for moving a pin held in a waiting position to a position on an optical axis of the optical detecting means, with the swing arm being operated by a swing means. A pin inserting means is included, which can be moved from the waiting position into the pin inserting side of the swing arm on the optical axis, with the pin inserting means being rotationally moved by the swing means through a transmitting means.