1. A sync detector, comprising: a correlation computing unit configured to receive signal values corresponding to respective sample points and to compute auto-correlation of the received signal values between sample points of interest and sample points that are situated at a distance equal to a constant number of sample points from the sample points of interest; a correlation value synthesizing unit configured to receive auto-correlation values corresponding to respective sample points obtained by the correlation computing unit and to synthesize the auto-correlation values with respect to at least two sample points among sample points that are spaced apart by the constant number of sample points thereby to compute a synthesized correlation value; and a peak-point detecting unit configured to detect a position of a sample point corresponding to a largest synthesized correlation value among synthesized correlation values corresponding to respective sample points obtained by the correlation value synthesizing unit.