To provide a cord length adjuster which is capable of making a long cord shorter for use and regulating it in length without cutting it short.

An opening 2 is provided to the two lateral inner walls of a case 1 opposed to each other, symmetrical supports 3 are provided to the inner base 4 of the case 4, and a lid 5 is provided to the upside of the case 1. When the case 1 is used as an existing relay cord length adjuster, the relay cord is wound on the support 1 and housed in the case 1, and then the case 1 is covered with the lid 5. When the relay cord is used, the cord wound on the support 3 in the case 1 is wound off and pulled out through the opening 2, whereby the cord can be extended as long as required. The cord pulled out through the opening 2 is wound on the support 3, whereby it can be set short in length.