A signal processing apparatus for determining whether a receiving signal is a target signal is provided. The apparatus includes: a sampling device for sampling the receiving signal to generate a plurality of sampled values; a first calculation device, coupled to the sampling device, for generating a plurality of first values according to the sampled values and a plurality of reference values; a second calculation device, coupled to the first calculation device, for grouping the first values into a plurality of value groups, respectively calculating the value groups to generate a plurality of second values and generating a determination value by calculating the second values; and a determination device, coupled to the second calculation device, for determining whether the receiving signal is the target signal by comparing the determination value with a threshold value.