It is an object of the invention to provide a circuit board for mounting a semiconductor chip and a manufacturing method thereof that prevent post-reflow warping and prevent peeling of the semiconductor chip and breakage resulting from thermal stress. In the circuit board for mounting a semiconductor chip, wiring regions, in which are formed wirings electrically connected to a semiconductor chip, are disposed on an insulating substrate in a vicinity of a chip region in which the semiconductor chip is mounted. A reinforcement layer, in which is formed reinforcement layers for reinforcing the insulating substrate, is disposed in a vicinity of the wiring regions.