A contact terminal having a main body case and a plunger pin received in an elongate hole formed in the main body case is provided. The plunger pin is a round bar provided with a step and includes a small diameter portion including the protrusion end portion and a large diameter portion that slides on a surface of the hole to freely move in a longitudinal direction thereof. A cut space is formed to extend from an end of the large diameter portion so as to leave at least a part of a side surface portion of the large diameter portion and the cut space receives an insulation ball including at least an insulation surface. A coil spring is arranged between the hole and the insulation ball to press the protrusion end portion of the plunger pin such that the protrusion end portion protrudes from the main body case.