It is well known that the amplitude of the gravitational wave (GW) produced during inflation is proportional to the energy scale of inflation. However, it is true only if (i) GW is described by Einstein theory (GR) and (ii) the GWs from vaccum fluctuation is dominant. I will discuss the cases where the above two conditions are not satisfied. In particular, I will explain the new model in which the axion-SU(2) coupled system generates GW during inflation and its observational consequence.