A shutter unit capable of preventing the scattering of the laser beam upon closing the optical path of the laser beam and capable of being miniaturized, and a laser processing device employing such a shutter unit. In a shutter unit 1, when the optical path of the laser beam L is opened, a rotating member 57 is rotated around an axis line .gamma., and an opening 61 is positioned on an optical axis .alpha. so as to pass the laser beam L therethrough. Meanwhile, when the optical path of the laser beam L is closed, the rotating member 57 is rotated and a reflective surface 62 is positioned on the optical axis .alpha. so as to reflect the laser beam L. Here, since the reflected laser beam L is absorbed by an optical absorption member 63, it is possible to prevent the scattering of the laser beam L when the optical path of the laser beam L is closed. In addition, since the opening 61 and reflective surface 62 are both formed on the rotating member 57 which rotates around the axis line .gamma. that is substantially orthogonal to the optical axis .alpha., it is possible to reduce the size of the shutter unit 1.