A connector has signal contacts and ground contacts, each of which includes a contact portion to be connected with a mating connector. In a predetermined plane, the contact portions of the signal contacts and the contact portions of the ground contacts are grouped and arranged into a first line and a second line. In the predetermined plane, four specific signal contact portions are surrounded by four specific ground contact portions. The four specific signal contact portions are the contact portions of the signal contacts constituting two pairs. The four specific ground contact portions are two of the contact portions of the ground contacts belonging to the first line and two of the contact portions of the ground contacts belonging to the second line. In the predetermined plane, a minimum distance between two of the specific ground contact portions is smaller than another minimum distance between one of the specific signal contact portions and one of the contact portions of the signal contacts other than the specific signal contact portions.