To provide a wire stripper capable of efficiently stably forming a stripping margin at all times irrespective of the length of a wire or the stripping margin, and preventing the wire from extending.

This wire stripper 1 is provided with a clamping means 3 for clamping one end of a wire W to pull it out, a wire cutting means 5 for cutting the wire W into a predetermined length, a sheath cutting means 7 for cutting only a sheath D of the other end of the wire W into a predetermined length, and a stripping margin forming means 9 for removing the sheath D of the other end to expose a core material E. The stripping margin forming means 9 is provided with a stripping means 67 for sandwiching a portion near to the cut position of the sheath D and stripping it, and a pair of vertical wire sandwiching means 65, 69 integrally moving by an uneven engaging structures 79, 81 based on a power transmitted from the stripping means 67. The wire cutting means 5, the sheath cutting means 7 and the stripping margin forming means 9 are provided so as to be vertically paired so that an upper unit 23 and a lower unit 25 can be integrally approximate or separate.