An apparatus for time synchronization of an orthogonal frequency division multiplexing (OFDM) system oversamples a received signal using a master clock having a frequency at least four times higher than a minimum sampling frequency in a transmission apparatus, sets one of a plurality of oversampled signals to an on-time signal, and shifts each of the remaining oversampled signals by a predetermined time on the basis of the on-time signal. The apparatus for time synchronization calculates a correlation value by correlating each of the shifted signals and the on-time signal with a previously known signal, detects a maximum energy value among the calculated correlation values, and detects a start point of a frame by comparing the maximum energy value with a predetermined threshold value.