A fuel cartridge (1) includes a fuel storage container (2), and a fuel supply port (4) for taking out a fuel stored in the fuel storage container (2). The fuel supply port (4) is provided with a fuel supply port protecting mechanism. The fuel supply port protecting mechanism includes a door (10) for opening/closing an opening (11) provided between the fuel supply port (4) and an outside, and a lock mechanism (20) for locking the door (10) so that the door (10) does not open. This can prevent, with the fuel cartridge not installed on a fuel cell, the leakage of a fuel from the fuel cartridge caused by improper handling by a user, etc.