An image-forming apparatus provided with an image-forming portion in a casing, including: a casing frame forming a skeleton of the casing; a shield chassis portion formed so as to be partially integrated with the casing frame per se; and at least one board directly attached to the shield chassis portion and mounted with a power supply circuit, a control circuit and an image-processing circuit for permitting the image-forming portion to execute an image-forming process. A frame structure per se of the image-forming apparatus (an embodiment in which the shield chassis portion is formed so as to be integrated with the casing frame per se) or a method for producing the frame structure is also a subject of the invention.