A new 40 m Small Angle Neutron Scattering (SANS) instrument was constructed, and has been opened to outside users since November 2010 at HANARO, Korea. The instrument is equipped with state-of-the-art components, and the performance of the instrument is comparable to that of advanced SANS instruments. The flux at the sample position is measured as 2.9×10⁷/cm² s with a wavelength of 5 Å and a collimation length of 1.7 m. The Q-range of the instrument covers from 0.0007 to 1.1 Å⁻¹ when the lens option is applied. In this paper, the design and characteristics of the 40 m SANS instrument are described, and data showing their performance are presented.