PURPOSE: To provide a wiring substrate capable of firmly coating an insulating substrate with wiring conductors whereto electric signals can be rapidly propa gated.

CONSTITUTION: This substrate wherein an insulating base substrate 1 is coated with wiring conductors is characterized by the insulating base substrate 1 formed of a mullite sintered body containing mullite exceeding 90.0volume% as well as the wiring conductors 5 formed of tungsten particles in particle diameter distribution as shown below, i.e., the tungsten particles of not exceeding 10.0wt.% in particle diameter not exceeding 1.0μm, 50-70wt.% in particle diameter of 1.03.0μm and not exceeding 5.0wt.% in particle diameter exceeding 5.0μm.