A jamming detector and jamming detecting method are disclosed. In accordance with the present invention, distribution of a received signal is compared with a reference distribution of a specific signal model. Deviation of the signal distribution from the reference distribution can be obtained according to the comparison results. The existence of jamming is determined according to the deviation. If the signal distribution significantly deviates from the reference distribution, it means that jamming exists. An anti-jamming circuit or algorithm can be activated only when jamming is detected, thereby power consumption is reduced.