To reduce an amount of concrete remaining in a hopper, improve the suction efficiency, and facilitate washing.
An inner bottom face 1d of a hopper 1 is formed like a circular arc along oscillation locus of an oscillation pipe 6 centered on an oscillation shaft 8. Filler blocks 15a, 15b scooping concrete up are attached to both side parts of the oscillation pipe 6 so as to overhang symmetrically to the right and left. A lower face of the filler block 15a is a circular arc face 16 sliding with a minute clearance ΔS on the inner bottom face 1d of the hopper 1, and an upper face thereof is a suction flow passage face 17 like recessed face. When the oscillation pipe 6 coincides with a suction discharge port 2b, the filler block 15b corresponds to a suction discharge port 2b, and when the oscillation pipe 6 coincides with the suction discharge port 2b, the filler block 15a corresponds to the suction discharge port 2a.