A probe unit includes: contact probes; and a probe holder, each of the contact probe including a plunger and a spring coil, each of the plunger including: a contact portion contacting an electrode of a contacted body; a flange portion extending from a base end of the contact portion and having a diameter larger than a diameter of the contact portion; a boss portion extending from an end of the flange portion different from an end continuing to the contact portion and having a diameter smaller than the diameter of the flange portion; and a base end portion extending from an end of the boss portion different from an end continuing to the flange portion and having a substantially same diameter with the boss portion.