A nucleic acid molecule that can bind to HMGB1 protein and applications thereof are provided. A nucleic acid molecule having a dissociation constant for HMGB1 protein of 5×10−7 or less can be used as the nucleic acid molecule that can bind to HMGB1 protein. The HMGB1 binding nucleic acid molecule can bind to HMGB1 protein that is known to be a cause of diseases such as cancer and inflammation, and it is therefore possible to obtain an effect to prevent and an effect to treat such diseases by allowing the HMGB1 binding nucleic acid molecule to bind to HMGB1 protein in a living body.
