An optical probe comprising: a laser light source that emits laser light; a collimator lens that converts the laser light emitted from the laser light source into parallel light; a light shape changing section that allows the parallel light to change shape into linear laser light; an irradiating section to irradiate an object to be measured with a selected part of the linear laser light; an image pickup section that picks up an image of the object based on the laser light reflected from a surface of the object irradiated with the selected part of the linear laser light; and a controller that controls irradiation of the linear laser light by the irradiating section, wherein the linear laser light is composed of a plurality of parts including one end part and the other end part; and wherein the controller controls the irradiating section so that the irradiating section irradiates the object with the parts of the linear laser light sequentially from the one end part to the other end part characterized in that the controller is adapted to determine whether a picked-up image position obtained by the image pick-up section has changed from a last picked-up image position by a predetermined threshold value or more; and wherein, when the controller determines that the picked-up image position has changed from the last picked-up image position by the predetermined threshold value or more, the controller is adapted to determine that a virtual image due to multiple reflections of the linear laser light onto the work exists, and to prevent a part of the linear laser light from travelling toward the object, the part of the linear laser light causing formation of the virtual image. a laser light source that emits laser light; a collimator lens that converts the laser light emitted from the laser light source into parallel light; a light shape changing section that allows the parallel light to change shape into linear laser light; an irradiating section to irradiate an object to be measured with a selected part of the linear laser light; an image pickup section that picks up an image of the object based on the laser light reflected from a surface of the object irradiated with the selected part of the linear laser light; and a controller that controls irradiation of the linear laser light by the irradiating section, wherein the linear laser light is composed of a plurality of parts including one end part and the other end part; and wherein the controller controls the irradiating section so that the irradiating section irradiates the object with the parts of the linear laser light sequentially from the one end part to the other end part characterized in that the controller is adapted to determine whether a picked-up image position obtained by the image pick-up section has changed from a last picked-up image position by a predetermined threshold value or more; and wherein, when the controller determines that the picked-up image position has changed from the last picked-up image position by the predetermined threshold value or more, the controller is adapted to determine that a virtual image due to multiple reflections of the linear laser light onto the work exists, and to prevent a part of the linear laser light from travelling toward the object, the part of the linear laser light causing formation of the virtual image.