Provided is a measuring apparatus that includes: a semiconductor laser device that emits a laser light beam to an object to be measured； a driving unit that provides a driving signal for modulation drive of the semiconductor laser device； a first detection unit that detects a first electrical signal that corresponds to the intensity of the laser light beam modulated due to the self-coupling effect, in a first half-cycle of the driving signal； a second detection unit that detects a second electrical signal that corresponds to the intensity of a second laser light beam modulated due to the self-coupling effect, in a second half-cycle of the driving signal being in an opposite phase of the first half-cycle； a calculation unit that calculates a difference between the first and second electrical signals； and a measuring unit that measures a change in the state of the object based on the calculated difference.
