To provide an offset printing device suitable for forming a function element pattern of an electronic apparatus wherein a pattern can be printed uniformly within a printing face and printing of excellent length precision can be done, and to provide an image forming device formed by using a thick film circuit substrate whose element is formed by said printing device.

A blanket cylinder 101 having a suction and exhaust blowhole 103a on its curved face and a pressure adjusting machine 105 are provided. Thus, gas is sent in between the blanket cylinder 101 and a blanket so as to eliminate a contact between the blanket cylinder 101 and the blanket, so that the blanket is tensioned by a fixed tensile force so as to eliminate irregularity in the thickness of the blanket. Further, by reducing the pressure in between the blanket cylinder 101 and the blanket, the blanket cylinder 101 and the blanket are sucked, so that slack of the blanket at the time of continuous printing can be eliminated and swelling of the blanket can be also eliminated.