A method of manufacturing a package-on-package device includes a bonding step carried out by a bonding apparatus including a pressing member and a light source that produces a laser beam. A bottom package including a lower substrate, lower solder balls alongside an edge of the lower substrate, and a lower chip on a center of the lower substrate is provided, the bottom package is bonded to an interposer substrate having upper solder balls aligned with the lower solder balls, and a top package having an upper substrate and an upper chip on the upper substrate is bonded to the interposer substrate. While the interposer substrate is disposed on the bottom package, the pressing member presses the interposer substrate against the bottom package, and the laser beam adheres the lower solder balls to the upper solder balls.