Although the Higgs boson, which was predicted in the standard model (SM) of the particle physics, was discovered at LHC, we have not yet understood the dynamics of electroweak symmetry breaking. The SM has the minimal Higgs sector with one doublet field, though there is no principle to explain such a shape of the Higgs sector. In the models with the extended Higgs sector, the first order phase transition (1stOPT) at the electroweak symmetry breaking can be realized. We discuss spectra of gravitational waves (GWs) which are originated by the 1stOPT. We show that the models with the extended Higgs sector can be tested by measuring the characteristic spectra of the GWs at future interferometers such as LISA and DECIGO.