The present invention provides a Au-Sn-Bi alloy thin film which is uniform and thin while maintaining good bonding performance as a bonding layer using an Au-Sn-Bi alloy on a metalized layer on a substrate or an LED element. In the present invention, using an Au-Sn-Bi alloy powder paste obtained by mixing 15 to 30 wt% of RA flux and an Au-Sn-Bi alloy powder having a grain diameter no greater than 10 [mu]m and having a composition containing 20 to 25 wt% of Sn and 0.1 to 5.0 wt% Bi, with the remainder made up of Au, screen-printing is performed on a predetermined region on an Au metalized layer. Next, the Au-Sn-Bi alloy powder is melted by heating and then solidified. An An-Sn-Bi alloy thin film having a thickness no greater than 5 [mu]m and being provided with at least a eutectic structure is thereby formed.