It is possible to provide a technique capable of attaching a reactor to a power source unit even upon shipping a package containing an image forming apparatus from a factory as well as opening the package and installing the image forming apparatus in a place for installment, by optionally attaching the reactor to the power source unit.An image forming apparatus includes a case to accommodate a main body of the image forming apparatus and having a bottom portion; and a power source unit provided with at least an AC filter unit and a DC output circuit unit, and a reactor space disposed in the bottom portion of the case, the reactor space being a space for installing a reactor between the AC filter unit and the DC output circuit unit.