A structure of a panel which can be thinned down to about a panel thickness of a PDP and a manufacturing method thereof are provided. The image forming apparatus includes a photosensitive drum, and a beam scanning device including a plurality of semiconductor lasers which emit light beams for exposing the photosensitive drum, and a memory which stores first correction data for correcting the light amount of each light beam in a manner associated with each of the plurality of semiconductor lasers. Bids are received from one or more participants, each bid including information corresponding to the selected categories. The contaminant collection unit includes a coil and a collection container. A photoresist pattern is formed on the hard mask layer.