Abstract: A differential transmission connector unit is disclosed that includes a first differential transmission connector including a first electrically insulating block body; and first signal contact pairs and first ground contacts arranged alternately in a row in the first block body; and a second differential transmission connector including a second electrically insulating block body; and second signal contact pairs and second ground contacts arranged alternately in a row in the second block body. The first differential transmission connector is connected to the second differential transmission connector with the first signal contact pairs and the second signal contact pairs being in contact with each other and the first ground contacts and the second ground contacts being in contact with each other. One of the contact surface of each first ground contact and the contact surface of the corresponding second ground contact is a rolled surface, the contact surfaces contacting each other.