Three-dimensional scanner and robot system

A three-dimensional scanner (1) according to one aspect of the embodiments includes an irradiation unit (2), an imaging unit (3), a position detecting unit (42), and a scanning-region determining unit (43). The irradiation unit (2) emits a slit-shaped light beam while changing an irradiation position with respect to a measuring object. The imaging unit (3) sequentially captures images of the measuring object irradiated with the light beam. The position detecting unit (42) detects a position of the light beam in an image captured by the imaging unit (3) by scanning the image. The scanning-region determining unit (43) determines a scanning region in an image as a scanning target by the position detecting unit (42) based on a position of the light beam in an image captured by the imaging unit (3) before the image as a scanning target.