An electrical connector comprising: a housing for retaining a plurality of female contacts and a plurality of wires connection springs for connecting electric wires to those contacts; and lock arms for catching an object to be mated with the connector, each lock arm has; an arm main body integrally formed with the housing, the arm main body comprising a rear end portion, the rear end portion comprising an attachment portion configured for attachment to a releasing operation portion, the attachment portion comprising a vertical wall protruding from a surface of the rear end portion; characterised in that a rectangular plate-like horizontal wall is supported at an upper end of the vertical wall and is extending perpendicular to the vertical wall; the connector further comprises the releasing operation portion formed separately from the housing; wherein the releasing operation portion has a plurality of recesses and respectively receives in plural said recesses the horizontal walls of the attachment portions of the arm main bodies to be joined by the releasing operation portion and as a result of relative sliding with respect to the arm main body in a frontward/rearward direction, perpendicular to a direction in which the arm main bodies are adjacent to each other at least two adjacent arm main bodies are joined by the releasing operation portion, the releasing operation portion has a disengagement restriction portion for restricting disengagement of the attachment portion from the recess. a housing for retaining a plurality of female contacts and a plurality of wires connection springs for connecting electric wires to those contacts; and lock arms for catching an object to be mated with the connector, each lock arm has; an arm main body integrally formed with the housing, the arm main body comprising a rear end portion, the rear end portion comprising an attachment portion configured for attachment to a releasing operation portion, the attachment portion comprising a vertical wall protruding from a surface of the rear end portion; characterised in that a rectangular plate-like horizontal wall is supported at an upper end of the vertical wall and is extending perpendicular to the vertical wall; the connector further comprises the releasing operation portion formed separately from the housing; wherein the releasing operation portion has a plurality of recesses and respectively receives in plural said recesses the horizontal walls of the attachment portions of the arm main bodies to be joined by the releasing operation portion and as a result of relative sliding with respect to the arm main body in a frontward/rearward direction, perpendicular to a direction in which the arm main bodies are adjacent to each other at least two adjacent arm main bodies are joined by the releasing operation portion, the releasing operation portion has a disengagement restriction portion for restricting disengagement of the attachment portion from the recess. an arm main body integrally formed with the housing, the arm main body comprising a rear end portion, the rear end portion comprising an attachment portion configured for attachment to a releasing operation portion, the attachment portion comprising a vertical wall protruding from a surface of the rear end portion; characterised in that a rectangular plate-like horizontal wall is supported at an upper end of the vertical wall and is extending perpendicular to the vertical wall; the connector further comprises the releasing operation portion formed separately from the housing; wherein the releasing operation portion has a plurality of recesses and respectively receives in plural said recesses the horizontal walls of the attachment portions of the arm main bodies to be joined by the releasing operation portion and as a result of relative sliding with respect to the arm main body in a frontward/rearward direction, perpendicular to a direction in which the arm main bodies are adjacent to each other at least two adjacent arm main bodies are joined by the releasing operation portion, the releasing operation portion has a disengagement restriction portion for restricting disengagement of the attachment portion from the recess.