Provided is a flux activator containing a halogen compound represented by formula 1 below: where X1 and X2 represent different halogen atoms, R1 and R2 are each a group represented by any one of formulas —OH, —O—R3, —O—C(═O)—R4, and —O—C(═O)—NH—R5, R1 and R2 optionally represent the same group or different groups, R3, R4, and R5 are each an aromatic hydrocarbon group having 1 to 18 carbon atoms or an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and R3, R4, and R5 optionally represent the same group or different groups.