To take out a sample from a space where the sample of powdery substance flows without disturbing a surface of the sample by a pressure change in the space.

The apparatus is provided with a rotary plate 2 at a part penetrating a wall body 4 defining a space where a powdery substance flows and coming in and out of the wall body 4. The rotary plate 2 has a sample chamber 5 which is a hole of a predetermined depth to store a sample of the powdery substance. Moreover, a bottom plate 3 is provided to open/close a bottom of the sample chamber 5 in accordance with the rotation of the rotary plate 2. At least when the wall body 4 moves from the inside to the outside and from the outside to the inside, an upper lid 1 of the apparatus tightly closes the sample chamber 5 in cooperation with the bottom plate 3. A scraper part scrapes and uniforms the accumulated powdery sample leaking out of the sample chamber 5 in accordance with the rotation of the rotary plate 2. The bottom plate 3 opens the bottom of the sample chamber 5 when the sample chamber 5 moves from the outside of the wall body 4 to the inside, and shuts the bottom of the sample chamber 5 at least immediately after the sample chamber 5 comes out of the wall body 4 before the sample chamber comes outside and while the sample chamber 5 is outside the wall body 4.