Provided are an orthogonal frequency division multiplexing (OFDM) receiving apparatus and a mode detecting method thereof. The mode detecting method includes: detecting a first mode of a received signal by using first delay signals obtained by delaying the received signal, and first correlation values of the received signal; and detecting a second mode of the received signal by using second delay signals obtained by delaying a first correlation value corresponding to the first mode from among the first correlation values, and the first correlation value corresponding to the first mode. According to the OFDM receiving apparatus and the mode detecting method, a fast Fourier transform (FFT) mode is detected first and then a guard interval (GI) mode is detected based on a result of detecting the FFT mode from the same signal, and thus mode detection is accurately and quickly performed and the OFDM receiving apparatus has a reduced chip size.