A device for testing string tension in the stringing of a tennis racket of simplified construction as compared to prior art devices. The device comprises only five component parts, and occupies a minimum amount of storage space when not in use. Provision is made in several embodiments for including in measurement that component of tension which is caused by slight flexing of the tennis racket frame, and components of frictional force caused by engagement of the device with the tennis racket are completeley eliminated.