Provided is a quaternary Pb-free solder composition incorporating Sn—Ag—Cu—In, which can prevent a cost increase and sufficiently ensure proccessability and mechanical property as a solder material. To this end, indium (In) with appropriate amount is added into the Pb-free solder composition, and the addition amount of Ag is optimized, thus preventing a decrease in wettability caused by a decrease in the amount of Ag and improving resistance to a thermal cycling and a mechanical impact. The quaternary Pb-free solder composition includes silver (Ag) of about 0.3 wt. % or more, and less than about 2.5 wt. %, copper (Cu) of about 0.2 wt. % or more, and less than about 2.0 wt. %, indium (In) of about 0.2 wt. % or more, and less than about 1.0 wt. % or less, and a balance of tin (Sn).
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