A coupling method of coupling a flexible flat cable to a connector by a robot, includes a preparation step of preparing the connector having an insertion hole into which the flat cable is inserted and a seat having an introduction surface placed at a front side of the insertion hole and continuously coupled to the insertion hole, a first moving step of gripping the flat cable and moving the flat cable to a position facing the seat; and a pressing step of bringing the flat cable into contact with the introduction surface in a posture inclined relative to the seat with an end of the flat cable facing the insertion hole side and pressing the flat cable against the introduction surface, and moving the end toward the connector side.