A socket for a connector, the socket comprising: a socket housing having substantially a rectangular shape having a width in a width direction and a length in a longitudinal direction, a socket-side signal terminal disposed in the socket housing, a socket-side power source terminal disposed in the socket housing, and a socket-side holder bracket disposed in the socket housing; wherein, while the socket housing is engaged with a header housing, the socket-side signal terminal contacts a header-side signal terminal, and the socket-side power source terminal contacts a header-side power source terminal, wherein the socket-side holder bracket includes a mounting terminal configured to be soldered to a circuit pattern formed on a circuit board, wherein the socket-side power source terminal includes a base part configured to be soldered to the circuit pattern formed on the circuit board, and wherein the mounting terminal and the base part are configured to be soldered to a common circuit pattern, wherein the base part of the socket-side power source terminal protrudes from a side surface of the socket housing and the mounting terminal protrudes from the side surface, and wherein - the socket-side signal terminal and the socket-side power source terminal are arranged in the longitudinal direction of the socket housing, - a width of the socket-side power source terminal in the longitudinal direction of the socket housing is larger than a width of the socket-side signal terminal in the longitudinal direction, characterized in that the socket-side holder bracket and the socket-side power source terminal are adjacent to each other. a socket housing having substantially a rectangular shape having a width in a width direction and a length in a longitudinal direction, a socket-side signal terminal disposed in the socket housing, a socket-side power source terminal disposed in the socket housing, and a socket-side holder bracket disposed in the socket housing; wherein, while the socket housing is engaged with a header housing, the socket-side signal terminal contacts a header-side signal terminal, and the socket-side power source terminal contacts a header-side power source terminal, wherein the socket-side holder bracket includes a mounting terminal configured to be soldered to a circuit pattern formed on a circuit board, wherein the socket-side power source terminal includes a base part configured to be soldered to the circuit pattern formed on the circuit board, and wherein the mounting terminal and the base part are configured to be soldered to a common circuit pattern, wherein the base part of the socket-side power source terminal protrudes from a side surface of the socket housing and the mounting terminal protrudes from the side surface, and wherein - the socket-side signal terminal and the socket-side power source terminal are arranged in the longitudinal direction of the socket housing, - a width of the socket-side power source terminal in the longitudinal direction of the socket housing is larger than a width of the socket-side signal terminal in the longitudinal direction, characterized in that the socket-side holder bracket and the socket-side power source terminal are adjacent to each other. - the socket-side signal terminal and the socket-side power source terminal are arranged in the longitudinal direction of the socket housing, - a width of the socket-side power source terminal in the longitudinal direction of the socket housing is larger than a width of the socket-side signal terminal in the longitudinal direction, characterized in that the socket-side holder bracket and the socket-side power source terminal are adjacent to each other.