In one embodiment, a turbine monitoring system includes a temperature measurer configured to sense a temperature of steam to be introduced to a steam turbine, and output a sensing result of the temperature. The system further includes an electrical output measurer configured to sense an electrical output of a generator driven by the steam turbine, and output a sensing result of the electrical output. The system further includes a computing module configured to compute an erosion quantity of a moving vane of the steam turbine with water drops, based on the sensing result of the temperature that is output from the temperature measurer and the sensing result of the electrical output that is output from the electrical output measurer. The system further includes an outputting module configured to output information that is based on the erosion quantity computed by the computing module.