Optical measuring device and optical measuring method

An optical measuring method comprising:

• emitting a scanning light, of which an optical axis parallelly moves in a direction vertical to the optical axis, to an object from an emission device, the object having a level difference in a direction vertical to the optical axis of the scanning light and vertical to a scanning direction of the scanning light;
• performing photoelectric conversion with respect to the scanning light after passing over the object, by using a light receiving element;
• calculating, when scanning of the scanning light includes a first time period where the scanning light is not interrupted by the object, a second time period where a part of the scanning light is interrupted by the level difference, and a third time period where the scanning light is interrupted by the object, from a voltage wave obtained from time change of an electrical signal that is output by the light receiving element in the second time period, a distance corresponding to a time range from a first edge with respect to a voltage value where the scanning light is not interrupted by the object and a second edge with respect to a voltage value where the scanning light is interrupted by the object, when a part of the scanning light is interrupted by the object for the time range,
• wherein, in the calculating, the level difference in the direction vertical to the optical axis of the scanning light is detected, based on the distance calculated in the calculating.