An optical writing device that forms an electrostatic latent image on a photoreceptor. The device includes a pixel-information acquiring unit, a line-pixel-information storage unit that stores the acquired pixel information corresponding to a plurality of lines for each main scanning line, a light source device that exposes the photoreceptor with a period corresponding to an N-fold sub-scanning direction resolution of the pixel information, a positional-shift-information storage unit that stores a positional shift information, a sub-line counting unit that counts a sub-line period, a reading-line selecting unit that performs N times of selection that determines which main scanning line is selected as the line from which the pixel information is read out, on the basis of a calculated value from the counted value of the sub-line period and the positional shift information, and a pixel-information reading unit.