A probe pin, comprising: a coil spring; a first plunger made from an electrically conductive material; and a second plunger made from an electrically conductive material, wherein the first plunger comprises a first major portion, a first elastic extension, a second elastic extension, wherein the first elastic extension and the second elastic extension extend from the first major portion in parallel in a longitudinal direction of the first plunger, wherein the first elastic extension and the second elastic extension have different lengths in the longitudinal direction, wherein the first elastic extension and the second elastic extension have respective first and second inner surfaces (12B, 13B) opposing each other, wherein the first inner surface of the first elastic extension has a first contact part, wherein the second inner surface of the second elastic extension has a guide projection projecting toward the first elastic extension, wherein the first contact part and the guide projection are spaced away from each other in the longitudinal direction; wherein the second plunger comprises: a second major portion, a second contact portion disposed adjacent the second major portion, and a guide slot disposed in a direction away from the second major portion with respect to the second contact portion, wherein the first plunger is inserted in an inside of the coil spring from a first end of the coil spring, and the second plungers is inserted in the inside of the coil spring from a second end of the coil spring, characterized in that: the first plunger and the second plunger are combined with each other with the guide projection engaged in the guide slot and with the first contact part forced in contact with the second contact portion, such that the first plunger is slidingly movable relative to the second plunger in the longitudinal direction while maintaining an electrical contact between the first contact part and the second contact portion of the first and second plungers (1, 2). a coil spring; a first plunger made from an electrically conductive material; and a second plunger made from an electrically conductive material, wherein the first plunger comprises a first major portion, a first elastic extension, a second elastic extension, a first major portion, a first elastic extension, a second elastic extension, wherein the first elastic extension and the second elastic extension extend from the first major portion in parallel in a longitudinal direction of the first plunger, wherein the first elastic extension and the second elastic extension have different lengths in the longitudinal direction, wherein the first elastic extension and the second elastic extension have respective first and second inner surfaces (12B, 13B) opposing each other, wherein the first inner surface of the first elastic extension has a first contact part, wherein the second inner surface of the second elastic extension has a guide projection projecting toward the first elastic extension, wherein the first contact part and the guide projection are spaced away from each other in the longitudinal direction; wherein the second plunger comprises: a second major portion, a second contact portion disposed adjacent the second major portion, and a guide slot disposed in a direction away from the second major portion with respect to the second contact portion, a second major portion, a second contact portion disposed adjacent the second major portion, and a guide slot disposed in a direction away from the second major portion with respect to the second contact portion, wherein the first plunger is inserted in an inside of the coil spring from a first end of the coil spring, and the second plungers is inserted in the inside of the coil spring from a second end of the coil spring, characterized in that: the first plunger and the second plunger are combined with each other with the guide projection engaged in the guide slot and with the first contact part forced in contact with the second contact portion, such that the first plunger is slidingly movable relative to the second plunger in the longitudinal direction while maintaining an electrical contact between the first contact part and the second contact portion of the first and second plungers (1, 2).