A signal generator has a signal creating and supplying unit which creates a test signal to be transmitted to a measurement object and a license management unit which manages a license of waveform data for use in creating the test signal by the signal creating and supplying unit. The license management unit includes a waveform data memory which stores a plurality of waveform data files, a usable file list taking unit which takes a usable file list for specifying a usable waveform data file authenticated for the signal generator, the usable file list being input from an outside section, a usable file list memory which stores the usable file list, a determining unit which determines whether or not a desired waveform data file is included in the usable file list stored in the usable file list memory, and a waveform data file reading and transferring unit which reads the specified waveform data file from the waveform data memory and transfers the specified waveform data file to the signal creating and supplying unit when the determining unit determines in the affirmative.