Blades 20A to 20D are formed such that arm portions 31A to 31D of electroconductive elongated members 30A to 30D are retained in place with the help of insulating plates 50A-1 to 50D-2, a housing 10 has formed therein holding portions 17A to 17D allowing for the above-mentioned blades 20A to 20D to be inserted from the rear, said holding portions 17A to 17D have formed therein guiding portions 17A-1 to 17D-1 guiding the insertion of the above-mentioned blades 20A to 20D from the rear with the help of guiding grooves 17A-3 to 17D-3 extending in the forward-backward direction, and movement of the above-mentioned blades 20A to 20D in the up-down direction within the guiding grooves 17A-3 to 17D-3 is restricted.