In an image reader that adopts an off-axial optical system, an adjustable imaging mirror and a CCD fixed to a highly rigid structure. Since the relative position between reflecting mirrors and imaging mirrors can be set highly accurately, adjusting only the CCD-mounting position allows a required specification of the read image to be met. The imaging mirror can easily be adjusted without distorting the reflecting surface when necessary. The reflecting mirrors, the imaging mirrors, and the CCD-mounting-position adjusting means are positioned directly to reflecting-mirror supporting sections, imaging-mirror supporting sections, and CCD supporting sections, which are integrated with a carriage casing, and fixed to them. The CCD is fixed to the carriage casing with the CCD-mounting-position adjusting means. An imaging mirror close to a diaphragm and adjacent to the image is supported by a mirror adjusting plate. The position of the imaging mirror is adjusted by displacing the mirror adjusting plate.