An exposure head for forming an image of a first resolution corresponding to an arrangement interval of a plurality of lower electrodes in a crossing direction or an image of a second resolution lower than the first resolution. A circuit portion includes an image data storage portion that is arranged on the substrate together with a plurality of lower electrodes and converts input image data into image data according to the resolution. By this, the same exposure head can be used for both high resolution images and low resolution images without degrading the image quality.