To provide a metal ball for a wiring substrate which is good in loading property and suitable for use for interlayer conduction of the wiring substrate.

The metal ball for the wiring substrate is constituted of 20 to 80 mass% of a sum of Ag and/or Cu and the balance Bi with inevitable impurities, and is solidified in a spherical shape of 0.03 to 0.5 mm in particle size, roundness of the metal ball being 5% of the particle size. Further, the metal ball for the wiring substrate preferably contains 45 to 75 mass% of Ag.