A loudspeaker diaphragm manufacturing apparatus of the present invention comprises; a paper tank, a pulp dispersion reservoir tank connected to the paper tank, a stirring means provided in the paper tank, a water inlet unit connected to the paper tank, a drain unit disposed under the paper tank, and a paper mold disposed at the bottom of the paper tank or in the drain unit, wherein a sectional area of the drain unit is larger than the plane area of the paper mold. The drain unit may be further provided with a water flow control plate in a draining direction of the paper mold. According to the manufacturing apparatus and the manufacturing method of the present invention, diaphragms with very uniform internal composition and diaphragms with intentionally varied internal composition in accordance with required sound characteristics can be mass-produced with good reproducibility.