There is provide a liquid-cooled integrated substrate which has reduced material cost and processing cost, is reduced in warpage (shape deformation) as an integrated substrate, and has excellent strength and heat radiation performance, and a manufacturing method of the liquid-cooled integrated substrate. There is provided a liquid-cooled integrated substrate 1 in which a metal circuit board 15 made of aluminum or an aluminum alloy is bonded to one surface of a ceramic substrate 10, one surface of a plate-like metal base plate 20 made of aluminum or an aluminum alloy is bonded to another surface of the ceramic substrate 10, and a liquid-cooling type radiator 30 composed of an extrusion material is bonded to another surface of the metal base plate 20, wherein a relation between a thickness t1 of the metal circuit board 15 and a thickness t2 of the metal base plate 20 satisfies t2/t1≧2 where the thickness t1 of the metal circuit board 15 is 0.4 to 3 mm and the thickness t2 of the metal base plate 20 is 0.8 to 6 mm.