To provide a powdery mud making material mixing device by which muddy water used for construction work is obtained effectively, in large quantities and in a short time without making it by agitation and without a vessel for agitation required and with labor not required at all.

To the rear end of a jet flow pipe 2 which a throat part 3 is provided with expanded pipe diameter parts on the outlet side and the inlet side to form, a water feeding port 5 is connected, and near the inlet of the throat part 3, a discharge port 6a of a jet nozzle 6 communicating with the water feeding port 5, allowing a vacuum chamber 4b to be formed near behind the discharge port 6a of the jet nozzle 6. And also a mud making material suction port 7 is connected to the side of the vacuum chamber 4b, and to the head of the jet flow pipe 2, a static mixing pipe 10 having a little larger diameter than the expanded pipe diameter on the outlet side of the restriction part 3 is connected, and on the inner wall surface of the mixing pipe 10, plural projecting bars 11 are provided.