A method of manufacturing a wire harness (1A, 1B, 1C, 1D) that includes an electric wire and an electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) covering the electric wire, one end side of the electric wire being provided with a large-dimension portion (4A, 4B, 8, 9, 10, 11) having a dimension larger than an inner dimension of the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H), the method comprising mounting the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) on the electric wire via steps, performed in a sequence set forth, of: shaping the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) made of shape-memory polymer into a tube shape devoid of a cut and a seam; expanding the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) which is heated to a temperature equal to or higher than a glass-transition point such that the inner dimension of the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) becomes larger than the dimension of the large-dimension portion (4A, 4B, 8, 9, 10, 11); while the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) is in an expanded state, cooling the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) to a temperature below the glass-transition point and solidifying the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H); mounting the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) on the electric wire by passing the large-dimension portion (4A, 4B, 8, 9, 10, 11) and the electric wire inside the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H); and reheating the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) to a temperature equal to or higher than the glass-transition point such that the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) is restored to the inner dimension obtained after the step of shaping. shaping the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) made of shape-memory polymer into a tube shape devoid of a cut and a seam; expanding the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) which is heated to a temperature equal to or higher than a glass-transition point such that the inner dimension of the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) becomes larger than the dimension of the large-dimension portion (4A, 4B, 8, 9, 10, 11); while the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) is in an expanded state, cooling the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) to a temperature below the glass-transition point and solidifying the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H); mounting the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) on the electric wire by passing the large-dimension portion (4A, 4B, 8, 9, 10, 11) and the electric wire inside the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H); and reheating the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) to a temperature equal to or higher than the glass-transition point such that the electric wire protection tube (3, 3B, 3C, 3D, 3E, 3F, 3G, 3H) is restored to the inner dimension obtained after the step of shaping.