A wiring board includes an insulating substrate and a wiring conductor. The insulating substrate includes a first layer having an upper surface and a lower surface and having a first content of aluminum oxide and containing mullite and a second layer stacked on the upper surface and/or the lower surface of the first layer and having a second content of aluminum oxide greater than the first content. The wiring conductor is located inside the first layer and contains a manganese compound and/or a molybdenum compound. A manganese silicate phase and/or a magnesium silicate phase in an interface area between the insulating substrate and the wiring conductor.