The present invention relates, in general, to a joint channel and frequency offset estimation apparatus and method based on a multi-band-orthogonal frequency division multiplexing system, and, more particularly, to a joint channel and frequency offset estimation apparatus and method based on an MB-OFDM system, which uses low-rank LMMSE channel estimation, in which a low-rank is applied to the MB-OFDM system, thus decreasing complexity, and adds a simple structure using the autocorrelation characteristics of an estimated channel, thus joining channel estimation to frequency offset estimation at low complexity.The apparatus includes a channel estimator for receiving a Fourier-transformed OFDM signal, and calculating results of channel estimation using a Linear Minimum Mean Square Error (LMMSE) channel estimation, which minimizes a Mean Square Error (MSE) between an actual channel value and an estimated channel value. An autocorrelation unit calculates an autocorrelation value using the results, which are calculated through the channel estimator, in which a frequency offset is considered. A frequency offset estimator calculates a frequency offset, having a maximum value calculated by the autocorrelation unit, and estimating an actual frequency offset.