The present invention relates to a process of fusion-bonding a plastic film (8a, 8b) to an object to be fusion-bonded such as a port member (16) in manufacturing a drug bag, and relates to a drug bag. The present fusion-bonding process comprises steps of disposing a heat generation element generating heat by absorbing infrared laser, on an opposite surface (8c) of the plastic film (8a, 8b) from the port member (16), or between the port member (16) and the plastic film (8a, 8b), pressing a press member (30a, 30b), which allows infrared laser to be transmitted therethrough, from a side of the plastic film (8a, 8b), and irradiating the infrared laser (L) to the heat generation element (24a, 24b) through the press member (30a, 30b).
