A printing apparatus controls an ejection timing of a printing unit such that a first distance becomes shorter than a second distance, where the first and second distances are distances in a scanning direction between a landing position at which an ink droplet lands on a printing medium in a case where the printing unit scans in a first direction and a landing position at which an ink droplet lands on the printing medium in a case where the printing unit scans in a second direction in first and second printing modes, respectively.

An optical scanning device includes: a light source that emits a laser beam modulated and driven according to an image forming signal; a scanning optical system that includes a polygon mirror to scan a surface of a photoconductor with the laser beam from the light source; a surface identifying unit that associates a sub-scanning position by the polygon mirror with each surface of the polygon mirror; and a light-amount adjusting unit that adjusts a light amount of the light source according to the sub-scanning position, for each surface of the polygon mirror.