A method for measuring blood sugar that is performed by an apparatus for measuring blood is provided. The method includes calculating color data from multiple skin regions of interest in a skin image, classifying a user's meal state into a pre-meal state or a post-meal state through analysis of acquired user information, estimating blood sugar by applying the calculated color data to a blood sugar regression linear equation corresponding to the classified user's meal state, and measuring robust blood sugar by weighted averaging the estimated blood sugar.