PURPOSE: To provide a mud sampling apparatus by which accumulated mud can be sampled without changing an accumulation situation and which can be handled easily.

CONSTITUTION: A mud sampling apparatus 1 is constituted of a hollow rod 2, of first differentdiameter sockets 3, 4, of a second different diameter socket 5, of a sampling tube 6 and of a water stop bolt 7. The hollow rod 2 is constituted of a plurality of rod formation members 11 and of a drainage member 12. When the rod-formation members 11 in the proper number of pieces are screwed, a desired length can be obtained. A plurality of drainage holes 12a are made in the drainage member 12. The water stop bolt 7 is moved upward inside the hollow rod 2 when a wire 8 is rolled up. On the other hand, when the wire 8 is loosened, the water stop bolt 7 is moved downward in the hollow rod 2, it is stopped at a point of time when a taper part 7c for the water stop part 7 agrees with a taper part 3c for the first different-diameter socket 3, and an upper-part opening 6a in the sampling tube 6 is closed.