A solder paste composition used in a solder precoating method of forming solder bumps by forming a dam around electrodes on a substrate, filling a solder paste composition on the electrodes within opening parts surrounded by the dam, and heating the solder paste composition filled, so that solder is adhered to the surfaces of the electrodes. The solder paste composition contains solder powder, which is of a particle size distribution in which particles having a particle size of below 10 .mu.m are present 16% or more, and a sum of the particles having a particle size of below 10 .mu.m and particles having a particle size of 10 .mu.m or more and below 20 .mu.m is 90% or more. This enables to suppress occurrence of bump defects, and form solder bumps of a uniform height with a high yield by a solder precoating method using the dam.