A huge amount of silicon sludge is disposed of from silicon wafer manufacture, and its reuse is a critical issue. In this study, silicon nanoparticle generation from sludge was explored by nanosecond-pulsed laser irradiation. The nanoparticle production efficiency from silicon sludge was compared with that from silicon wafers. The result showed that using silicon sludge as a laser irradiation target leads to a distinctly higher production efficiency of nanoparticles; the smaller the powder size of the silicon sludge, the higher the efficiency. The generated silicon nanoparticles were crystalline with sizes at the 10 nm level.