To detect a frequency with higher accuracy without making a device large nor complicated by using the hybrid of a highly accurate split (synthetic) ratio.

This discriminator is provided with a 1st 0° hybrid C4 which distributes an input signal, a delay line Ld which delays a signal, a 1st 90° hybrid C1 which distributes the signal delayed by the line Ld, a 2nd 0° hybrid C5 which distributes the signal (a), a 2nd 90° hybrid C2 which synthesizes the signal and a 3rd 90° hybrid C3. In such a case, the 2nd 90° hybrid C2 and the 3rd 90° hybrid C3 are 90° hybrids which distribute the signal into two signals having an equal level and are more accurate than the 1st 90° hybrid C1. That is, hybrids whose split ratio (a:a) is more accurate than that of the 90° hybrid C3 are used as the 90° hybrids C1 and C2.