A manufacturing method of a radiator-integrated substrate comprising one surface of a metal circuit board made of aluminum or an aluminum alloy that is bonded to one surface of a ceramic substrate, and a metal base plate, wherein one surface of the metal base plate made of aluminum or an aluminum alloy is bonded to another surface of the ceramic substrate, and another surface of the metal base plate is bonded to a radiator, the method comprising: bonding the metal circuit board and the metal base plate to the ceramic substrate to form a metal-ceramic bonded substrate; then arranging the metal base plate of the metal-ceramic bonded substrate on one surface of the radiator via a brazing material with the metal base plate overlapping with the one surface of the radiator; arranging a jig having a concave R surface on another surface of the radiator with the jig butting against the another surface of the radiator; bringing a jig having a convex R surface protruding toward the metal-ceramic bonded substrate into contact with another surface of the metal circuit board of the metal-ceramic bonded substrate; and heat-bonding the metal-ceramic bonded substrate and the radiator while pressurizing the metal-ceramic bonded substrate and the radiator by the jig having the concave R surface arranged on the radiator side and the jig having the convex R surface arranged on the metal-ceramic bonded substrate side, wherein the radiator is an extrusion member made of aluminum or an aluminum alloy and the radiator has a hollow inner space that is partitioned by partition plates into flow paths for cooling liquid, wherein bonding of the ceramic substrate and the metal circuit board and bonding of the ceramic substrate and the metal base plate are performed by a molten metal bonding method, and wherein a curvature radius R (mm) of the convex R surface and the concave R surface is 6500 ≦ R ≦ surface pressure (N/mm 2) × 2000 + 12000. bonding the metal circuit board and the metal base plate to the ceramic substrate to form a metal-ceramic bonded substrate; then arranging the metal base plate of the metal-ceramic bonded substrate on one surface of the radiator via a brazing material with the metal base plate overlapping with the one surface of the radiator; arranging a jig having a concave R surface on another surface of the radiator with the jig butting against the another surface of the radiator; bringing a jig having a convex R surface protruding toward the metal-ceramic bonded substrate into contact with another surface of the metal circuit board of the metal-ceramic bonded substrate; and heat-bonding the metal-ceramic bonded substrate and the radiator while pressurizing the metal-ceramic bonded substrate and the radiator by the jig having the concave R surface arranged on the radiator side and the jig having the convex R surface arranged on the metal-ceramic bonded substrate side, wherein the radiator is an extrusion member made of aluminum or an aluminum alloy and the radiator has a hollow inner space that is partitioned by partition plates into flow paths for cooling liquid, wherein bonding of the ceramic substrate and the metal circuit board and bonding of the ceramic substrate and the metal base plate are performed by a molten metal bonding method, and wherein a curvature radius R (mm) of the convex R surface and the concave R surface is 6500 ≦ R ≦ surface pressure (N/mm 2) × 2000 + 12000.