The present invention provides a high frequency coupler(2) comprising first and second coupler patterns(11, 12) each having an annular shape broken at one location and formed, facing each other, on the front and rear surfaces of a circuit board(10) consisting of a dielectric and being t thick. The terminals(11a, 11b) of the first coupler pattern(11) serve as unbalanced terminals, and the terminals(12a, 12b) of the second coupler pattern(12) serve as unbalanced terminals from which coplanar lines(41, 42) are led out along the rear surface and connected with a balanced antenna(5). Since the first and second coupler patterns(11, 12) are kept in an electrostatic capacity coupling state as well as in a magnetic induction coupling state, the coupler high in transmission efficiency in a broad band can be realized.