An electrical connector pair 1 includes a receptacle connector 1a and a plug connector 1b. The receptacle connector 1a includes a first partition wall 12a, and the plug connector 1b includes a second partition wall 12b. When the receptacle connector 1a and the plug connector 1b are fitted together, the first partition wall 12a partitions a portion of the boundary between a third holder and a fourth holder where the second partition wall 12b is not formed such that a first contact 10a and a third contact 10b cannot be seen from a second contact and a fourth contact.