A powdery sample forming apparatus, which is used for measuring a water content of powder and in which all operations from powder supply to powder discharge are automated, includes a vertically elongated housing which has a sample inlet port at an upper portion thereof and a sample discharge port at a lower portion thereof. A porous plate or a screen plate divides the housing into longitudinal compartments and a gate opens and closes a bottom portion of one of the divided compartments. A vertically movable press member in the compartment having the gate presses the sample against the gate. A window is formed in a side wall of the compartment having the gate and can be cleaned with air under pressure or a vacuum.