An apparatus for estimating carrier frequency offset includes an Mth-power circuit, a spectrum generating circuit, a spectrum adjusting circuit, a peak frequency determining circuit and a frequency offset determining circuit. The Mth-power circuit performs an Mth-power calculation on an input signal to generate an Mth-power calculation result. The spectrum generating circuit generates a spectrum according to the Mth-power calculation result. The spectrum adjusting circuit identifies a partial energy peak value in a partial frequency range from the spectrum, and increases the partial energy peak value to be higher than any other energy in the spectrum to generate an adjusted spectrum. The peak frequency determining circuit identifies a peak frequency having a maximum energy peak value from the adjusted spectrum. The frequency offset determining circuit determines an estimated carrier frequency offset result according to the peak frequency.