Abstract: The purpose of the present invention is to provide a heat-sealing device capable of preventing problems associated with cap sealing performance and/or sensation of the cap being open due to an inappropriate cap temperature.

Abstract: The purpose of the present invention is to provide a detection device that detects the occurrence of an event (so-called “double capping”) in which two caps are disposed on one container. To that end, the detection device (10, 10A) of the present invention has two types of sensors provided on a production line (100) for a commercial product in which an opening (1A) of a container (1) is sealed with a cap (2), said sensors being a proximity sensor (3) along a path where the container (1) moves and a sensor (4: for example, a transmission sensor) equipped with a transmitter (4A), which is inside the same path, and a receiver (4B). An area detected by the sensors (3, 4) is an area where the cap (2) is not present in a normal state (a state in which double capping has not occurred), but where a subsequent cap (2-1) is present if two caps (2) in a row have been attached to one container (1).