Optical interference measuring method

An optical interference measurement method comprising:

• dividing, by a light division unit, light emitted from a low coherence light source and adjusted at equal frequency intervals into measurement light and reference light;
• and
• obtaining a surface shape profile from an interference signal of interference light in which reflected light from a measurement object and the reference light are multiplexed after the measurement light enters the measurement object while scanning with a scanning mechanism is performed using the measurement light,
• wherein when the measurement light enters the measurement object, a range obtained by adding a measurement range determined by an interference light detection unit from a zero point overlaps with a range obtained by subtracting the measurement range from a distance from the zero point, the zero point being a point at which a signal optical path length light that is the measurement light and a reference optical path length of the reference light matches each other, the distance being a distance of a half of a value obtained by multiplying a reciprocal of a mode interval of an optical comb generation filter by a light speed, and
• a change amount of a distance between the scanning mechanism and the measurement object generated when the scanning with the scanning mechanism is performed exceeds twice the measurement range when the scanning with the scanning mechanism is performed.