Disclosed is a technology of producing quantum dots that are nano-size semiconducting crystals. A quantum dot producing apparatus includes a mixer for mixing precursor solutions, and a heating furnace with a plurality of heating areas providing different temperature conditions to heat the precursor mixture. Between the heating areas, a buffer may be installed which provides a low-temperature condition to prevent addition nucleation. Through this configuration, nucleation is separated from nuclear growth, uniformity in particle size of quantum dots is improved, which enables the mass-production of quantum dots, rather than a quantum dot producing apparatus with a single heating area that provides a constant temperature condition.