An optical processing apparatus includes: a housing; a stage; and a light irradiation unit configured to cause a light source unit to emit light so as to form a strip-like irradiation area extending over an area wider than a width of a substrate in a right and left direction. The stage and the light irradiation unit are moved by a moving mechanism relatively to each other in a back and forth direction. Light emitted from the light irradiation unit is deviated by a light-path changing unit from a relative movement area of a substrate. When a substrate is relatively moved below the light irradiation unit without the intension of being subjected to a light irradiation process, a control unit outputs a control signal such that an irradiation area is not formed on a surface of the substrate by the light-path changing unit, while the light source unit emitting light.