A portable image forming device which is moved on an original in a direction perpendicular to a primary scan direction for subscan, and divides original reflection light beams into picture pickup elements in the primary scan direction through an image forming optical system to imageform the pickup elements on a pickup device for reading. The pickup range of the pickup device in the primary scan direction is designed to be variable, and means for setting the pickup range is provided. With a portable copying machine which houses the pickup device and a printing section including a writing head in a single casing, paper is fed to the printer section as required by making use of the movement of the machine for original scan.