A laser scanner comprising a main base, a distance measuring optical assembly for measuring a distance to the object to be measured, a rotation irradiating assembly for performing the rotary irradiation of the distance measuring light, a case which accommodates the distance measuring optical assembly and the rotation irradiating assembly, and an adapter, wherein a case includes a case frame, a left case, and a right case, the case frame includes a lower frame portion, the lower frame portion includes a left partition and a right partition, a liquid-tight space to accommodate the distance measuring optical assembly is formed when the left case is mounted, and the distance measuring optical assembly is exposed when the left case is removed, liquid-tight space to accommodate the rotation irradiating assembly is formed when the right case is mounted, and the rotation irradiating assembly is exposed when the right case is removed.