The energy confinement degradation was found in the FT-1 Tokamak in ECRH experiments. The time evolution of Te profile during the ECRH pulse was measured by the laser scattering, and the local energy balance was analysed by a numerical code. The peripherical absorption of microwave power and the fast development of some additional energy loss mechanism due to the action of microwaves on the plasma are supposed to be the reasons for confinement degradation.