There is provided a wire for a reed switch used for a material of a reed piece comprised by a reed switch, the wire being composed of an iron-group alloy containing Fe and 0 mass % or more and less than 10 mass % of Ni, with a total content of the Fe and the Ni satisfying 10 mass % or more and less than 20 mass %, with a balance of Co and an impurity, the iron-group alloy having a cubic crystal structure, the wire having a Curie temperature of 900° C. or higher and a specific resistance of 15 μΩ·cm or less at normal temperature, a ratio of a thermal expansion coefficient of a glass tube comprised by the reed switch to a thermal expansion coefficient of the wire for the reed switch being 90% or more, the wire having a diameter of 1 mm or less.