A ceramic circuit substrate according to the present invention includes a ceramic substrate, a copper circuit made of a copper-based material bonded, via a bonding layer, to a surface of the ceramic, and a copper heat sink made of the copper-based material bonded, via a bonding layer, to the other surface of the ceramic. The bonding layers each include a brazing material component including two or more kinds of metals, such as Ag, and an active metal having a predetermined concentration. The bonding layers each include a brazing material layer including the brazing material component, and an active metal compound layer containing the active metal. A ratio of a bonding area of the active metal compound layer in a bonding area of each of the bonding layers is 88% or more.