A novel method for extending the frequency frontier in gravitational wave observations is proposed. It is shown that gravitational waves can excite a magnon. Thus, gravitational waves can be probed by a graviton-magnon detector which measures resonance fluorescence of magnons. Searching for gravitational waves with a wave length λ by using a ferromagnetic sample with a dimension l, the sensitivity of the graviton-magnon detector reaches spectral densities, around 5.4 × 10 −22 × ( l λ/2π ) −2 [Hz −1/2 ] at 14 GHz and 8.6 × 10 −21 × ( l λ/2π ) −2 [Hz −1/2 ] at 8.2 GHz, respectively.