A wire length-adjusting device provided with a wire replacement mechanism is configured to enable the replacement of a wire to be adjusted in length, the device facilitates replacing the wire to be adjusted in length. This device is provided with: a length-adjusting mechanism unit enabling a wire to be adjusted in length and fed on a feed path in design dimension increments; a plurality of wire support members for supporting a portion on one end of the wire in a configuration conforming to the feed path, the wire support members having a downstream guide unit for guiding the wire fed by the length-adjusting mechanism unit on a downstream-side wire path; and a movement mechanism unit capable of moving the plurality of wire support members between a setting position for disposing the supported wire on the feed path and a standby position different from the setting position. The downstream guide unit is disposed at a position downstream from the length-adjusting mechanism unit in a state where the wire support members are disposed in the setting position.