A connector includes a block and a required number of contacts held and fixed in the block. A plate-shaped piece made of a heat resistant and electrically insulating material is fixed to the block on that side of the contacts to which conductors are connected. The plate-shaped piece is preferably formed with grooves with a predetermined interval on that surface of the piece on which the contacts are arranged. With this construction, it is possible to provide an improved connector which is able to prevent the block from being deformed due to heating in soldering and welding when connecting conductors, and is free from any defective connection and failed insulation without raising the manufacturing and operating cost.