A disk cartridge in which a disk is loaded is formed with composite synthetic resin including at least two types of thermoplastic resin, an anti-static polymer, and an inorganic filler, heat-deforming temperatures of at least two types of the thermoplastic resin mutually differing. Each upper contact includes an upper connecting portion and an upper soldering portion. On-line measurement of the mass or volume of material contained in a specific region of interest of the manufactured items is performed 100% on-line.