To provide an unburnt carbon measurement instrument capable of conducting measuring or the like in a short period of time and a coal ash treatment apparatus to control separating ability of an unburnt carbon separation apparatus based on the measured signal of the instrument.

A complex permittivity of a coal ash sample is obtained by using a cavity resonator 22 and an unburnt carbon ratio is obtained from this complex permittivity and a functional equation of the unburnt carbon ratio and the complex permittivity obtained by using coal ash having known physical properties. Alternatively, the unburnt carbon ratio is obtained by using the cavity resonator and a waveguide to obtain a complex permittivity and a microwave phase difference of the coal ash sample, and using these with a functional equation of the unburnt carbon ratio and the complex permittivity and the phase difference obtained by using coal ash having known physical properties. Further alternatively, the unburnt carbon ratio is obtained by using the waveguide to obtain a phase difference and intensity difference of the microwave of the coal ash sample, and using these with a functional equation of the unburnt carbon ratio, the phase difference and the intensity difference obtained by using coal ash having known physical properties. And separating ability of the unburnt carbon separation apparatus is controlled by an operation control device based on the measured signal of these measurement instruments.