A reliability determination unit determines a measurement reliability on the basis of a point on a first parallax image. An imaging condition determination unit determines whether imaging conditions of an imaging unit have changed after the reliability determination unit determines that the measurement reliability is low. The imaging unit captures an image of an object which is a measurement target and generates a second parallax image after the reliability determination unit determines that the measurement reliability is low. The reliability determination unit determines the measurement reliability on the basis of a point on the second parallax image after the imaging condition determination unit determines that the imaging conditions have changed.
