Provided is a device for measuring continuous fastener chain lengths, the device being capable of applying a constant tension on the continuous fastener chain and stabilizing length measurement precision. The device (20) for measuring continuous fastener chain lengths is provided with: a length measurement unit (30) for measuring the feed length of a continuous fastener chain (C1); a tension-applying unit (40) for applying tension on the continuous fastener chain (C1); and a tension-detecting unit (50) for detecting the tension applied on the continuous fastener chain (C1). The tension-applying unit (40) keeps the tension applied on the continuous fastener chain (C1) constant on the basis of the tension detected by the tension-detecting unit (50).