A multiband high-frequency circuit comprising a first switch SPDT1 for switching the connections of a multiband antenna to transmitting circuits 11bg-T, 11a-T and receiving circuits 11bg-R, 11a-R of first and second communications systems, and a transmitting/receiving circuit BLT-TR of a third communications system, a diplexer circuit Dip1 for branching a high-frequency signal to 11a-R and 11bg-R or BLT-TR and a diplexer circuit Dip2 for branching a high-frequency signal to 11bg-T and 11a-T, both of which are disposed downstream of SPDT1, each diplexer circuit Dip1, Dip2 comprising a lower-frequency-side filter and a high-frequency-side filter, a bandpass filter BPF1 being disposed downstream of the lower-frequency-side filter of the diplexer circuit Dip1, and a second switch SPDT2 being disposed downstream of the bandpass filter BPF1.