A socket includes: a contact probe; and an insulating support body supporting the contact probe. The contact probe includes: a first plunger to be connected with an object to be inspected; a second plunger to be connected with an inspecting board; and a spring configured to urge the first plunger and the second plunger in a direction apart from each other. In a state where a tip end of the first plunger is released, a projecting amount of the second plunger from the insulating support body is zero with a natural length of the spring.