A circuit board is manufactured by filling a via-hole formed in an
insulating substrate with conductive material, disposing conductive
layers on both sides of the insulating substrate, and forming alloy of
component material of the conductive material with component material of
the conductive layers. In the circuit board, therefore, the conductive
material filled in the via-hole formed in the insulating substrate is
securely connected electrically as well as mechanically to the conductive
layers on both sides of the insulating substrate with high reliability.