An electromagnetic levitation technique performed in a static magnetic field was used to measure the density, surface tension, normal spectral emissivity, heat capacity, and thermal conductivity of molten SUS316L and SUS316L containing 5 mass% B4C. The addition of 5 mass% B4C to SUS316L yielded reductions of 111 K, 6%, 22%, and 8% in the liquidus temperature, density, normal spectral emissivity, and thermal conductivity at the liquidus temperature of SUS316L, respectively. Nevertheless, the heat capacity increased by 3% with this addition. Although the 5 mass% B4C addition had no clear effect on the surface tension, the sulfur dissolved in the SUS316L resulted in a significant decrease in the surface tension.