A boron nitride/resin composite circuit board having high heat dissipation characteristics and high relyability is provided. A boron nitride/resin composite circuit board, including: a plate-shaped resin-impregnated boron nitride sintered body having a plate thickness of 0.2 to 1.5mm, the plate-shaped resin-impregnated boron nitride sintered body including 30 to 85 volume% of a boron nitride sintered body having boron nitride particles bonded three-dimensionally, the boron nitride particles having an average long diameter of 5 to 50µm, and 70 to 15 volume% of a resin; and a metal circuit adhered onto both principal planes of the plate-shaped resin-impregnated boron nitride sintered body, the metal circuit being copper or aluminum, wherein: a ratio of a linear thermal expansion coefficient in a plane direction of the resin-impregnated boron nitride sintered body at 40 to 150°C (CTE1) and a linear thermal expansion coefficient of the metal circuit at 40 to 150°C (CTE2) (CTE1/CTE2) is 0.5 to 2.0.