SOCKET

A socket includes power-supply blade receivers and a grounding blade receiver for retaining power-supply plug blades and a grounding plug blade of a plug, respectively. Each of the power-supply blade receivers includes a power-supply retaining portion and a power-supply contact portion. The grounding blade receiver includes a grounding retaining portion and a grounding contact portion which is installed further on the upstream side in the insertion direction of the plug than a position which is spaced away from the power-supply contact portion to the downstream side in the insertion direction by less than the certain distance. The grounding retaining portion is spaced away by the certain distance or more from the power-supply retaining portion to the downstream side in the insertion direction.