A connector comprising: a first insulator substrate; a first contact configured by arranging a plurality of contact pins (14a, 14b, 14c, 14d) including contact pins for differential signals as an array, on a top surface of the first insulator substrate; a second insulator substrate; a second contact configured by arranging a plurality of contact pins (15a, 15b, 15c, 15d) including contact pins for differential signals as an array in the same direction as the array direction of the first contact, on an undersurface of the second insulator substrate; and a metal plate sandwiched by an undersurface of the first insulator substrate and a top surface of the second insulator substrate; wherein the contact pins for differential signals of the first contact and the contact pins for differential signals of the second contact are arrayed in the same order so as to face each other; characterized in that one or more short holes in an arbitrary shape and with a size smaller than a circle having a diameter corresponding to one-fourth of the wavelength of the differential signals are formed in an area on the metal plate, said area being sandwiched by, and disposed along, the contact pins (14b, 15b) for differential signals of the first and second contacts (14, 15) facing each other; and one or more long holes are formed in an area on the metal plate other than an area sandwiched by the differential signal pins of the first contact and the differential signal pins of the second contact, said pins facing each other, and said latter area where the long holes are not formed, being positioned on the leg-part (14a-2, 15a-2) side of points of contact with a counterpart connector; and rest positions in the first and second contacts (14, 15) that are in contact with contacts of a counterpart connector when the connector is fully engaged with the counterpart connector are defined as first contact points and second contact points, respectively; and the short holes are formed in an area other than an area sandwiched between the first contact points and the second contact points. a first insulator substrate; a first contact configured by arranging a plurality of contact pins (14a, 14b, 14c, 14d) including contact pins for differential signals as an array, on a top surface of the first insulator substrate; a second insulator substrate; a second contact configured by arranging a plurality of contact pins (15a, 15b, 15c, 15d) including contact pins for differential signals as an array in the same direction as the array direction of the first contact, on an undersurface of the second insulator substrate; and a metal plate sandwiched by an undersurface of the first insulator substrate and a top surface of the second insulator substrate; wherein the contact pins for differential signals of the first contact and the contact pins for differential signals of the second contact are arrayed in the same order so as to face each other; characterized in that one or more short holes in an arbitrary shape and with a size smaller than a circle having a diameter corresponding to one-fourth of the wavelength of the differential signals are formed in an area on the metal plate, said area being sandwiched by, and disposed along, the contact pins (14b, 15b) for differential signals of the first and second contacts (14, 15) facing each other; and one or more long holes are formed in an area on the metal plate other than an area sandwiched by the differential signal pins of the first contact and the differential signal pins of the second contact, said pins facing each other, and said latter area where the long holes are not formed, being positioned on the leg-part (14a-2, 15a-2) side of points of contact with a counterpart connector; and rest positions in the first and second contacts (14, 15) that are in contact with contacts of a counterpart connector when the connector is fully engaged with the counterpart connector are defined as first contact points and second contact points, respectively; and the short holes are formed in an area other than an area sandwiched between the first contact points and the second contact points.