A circuit board includes a metal substrate, a resin layer, an insulating layer, and a first conductive structure. The metal substrate has a first through hole, and the first through hole has a first width. A portion of the resin layer is disposed in the first through hole. The resin layer has a second through hole. The second through hole has a second width. The insulating layer is disposed on at least one surface of the metal substrate, and a portion of the insulating layer contacts the resin layer. The first conductive structure is disposed in the second through hole. The first conductive structure penetrates through the metal substrate. The first width is greater than the second width. A manufacturing method of the circuit board is also provided.