An object is to provide a connector with which a cable assembly with suppressed generation of a noise during high-speed signal transmission can be formed, and a cable assembly using the connector. The connector 10 of the present invention is characterized as follows. Specifically, the connector 10 includes: a substrate 11; multiple signal terminals 31, 32 provided parallel to each other on one surface of the substrate 11; and a ground layer 41 provided on another surface of the substrate 11. Each of the signal terminals 31, 32 and the ground layer 41 are disposed in such a manner that at least a portion of the ground layer 41 and at least a portion of each of the signal terminals 31, 32 are superposed on each other with the substrate 11 therebetween. Multiple holes 43 are formed in the portion of the ground layer 41 superposed on each of the signal terminals 31, 32. A largest diameter of each of the holes 43 is smaller than a distance L between the centers of the signal terminals adjacent to each other.