Parts built-in circuit board

PROBLEM TO BE SOLVED: To provide a component built-in circuit board which achieves high packaging density and thickness reduction.SOLUTION: A component built-in circuit board 100 includes a core layer 200 formed by a conductor layer in which a through hole 201 is formed, and a component 500 is disposed in the through hole 201. A signal line 610 which transmits a high frequency signal is formed in an area of a conductor layer 421 facing the core layer 200 in which the through hole 201 is projected in a thickness direction. The component 500 includes a ground conductor 510 which is formed in at least a part of an area formed by projecting the signal line 610 in the thickness direction and functions as ground.