This paper presents a method for estimating a spectral reflectance including near-infrared components. In the proposed method, we represent a model of pixel values calculation by a digital camera as a matrix operation and estimate a spectral reflectance by applying Non-negative Matrix Factorization. In addition, we calculate superpixels for reduction of noise effect and utilize spectral reflectance database for spectral estimation of light source in order to improve estimation accuracy. The effectiveness of the proposed method is shown through experiments using simulated reflectance and actual images.