There is provided a water-soluble flux composition for soldering which is excellent particularly in heat resistance and flux residues after soldering of which can be easily removed by washing with water or warm water. The flux composition for soldering contains a compound of formula (1): wherein R1, R2, R3, Rd4, R5 and R6 independently of one another are a hydrocarbon group or hydrogen atom, and A1, A2 and A3 independently of one another are hydroxy group or an organic group of formula (2): and at least one of A1, A2 and A3 is an organic group of formula (2).