A high-frequency device comprising a high-frequency circuit for transmitting and receiving signals for a plurality of communications systems, the high-frequency device comprising an integral laminate comprising plural dielectric layers having electrode patterns for said high-frequency circuit, and devices mounted on said laminate; said high-frequency circuit comprising first and second antenna terminals (Ant1, Ant2), a transmitting terminal (Tx_2.5G) and first and second receiving terminals (Rx_2.5G_1, Rx_2.5G_2) for a first communications system, a transmitting terminal (Tx_3.5G) and first and second receiving terminals (Rx_3.5G_1, Rx_3.5G_2) for a second communications system, and first and second switch circuits (SPDT1, SPDT2) each having a common terminal (c) and a plurality of switching terminals (1, 2); said first antenna terminal being connected to the common terminal (c) of said first switch circuit (SPDT1), and said transmitting terminal (Tx_2.5G) for the first communications system being connected to a first switching terminal of said first switch circuit (SPDT1); said second antenna terminal being connected to the common terminal (c) of said second switch circuit (SPDT2), and said transmitting terminal (Tx_3.5G) for the second communications system being connected to a first switching terminal of said second switch circuit (SPDT2); said first receiving terminals (Rx_2.5G_1, Rx_3.5G_1) for the first and second communications systems being connected to a second switching terminal of said first switch circuit (SPDT1) via a first receiving-side multiplexer circuit, which is adapted to branch signals for the first and second communications systems; said second receiving terminals (Rx_2.5G_2, Rx_3.5G_2) for the first and second communications systems being connected to a second switching terminal of said second switch circuit (SPDT2) via a second receiving-side multiplexer circuit, which is adapted to branch signals for the first and second communications systems; the first receiving-side multiplexer circuit and the second receiving-side multiplexer circuit each having a lowpass filter circuit constituted by a phase line (lda1, ldb1); and the lowpass filter circuit of each multiplexer circuit (DIP1, DIP2) being connected via a bandpass filter circuit (BPF4, BPF7) to the corresponding receiving terminal (RX_t.5G_1, Rx_2.5G_2) of the first communication system characterised in that at least one of said transmitting terminals (Tx_2.5G; Tx_3.5G) for the first and second communications systems is connected to its corresponding switch circuit (SPDT1, SPDT2) without a multiplexer therebetween; the first receiving-side multiplexer circuit and the second receiving-side multiplexer circuit each have a highpass filter circuit constituted by a phase line (lda2, ldb2); the highpass filter circuit of each multiplexer circuit (DIP1, DIP2) is connected to the corresponding receiving terminal of the second communication system (Rx_3.5G_1, Rx_3.5G_2) via a bandpass filter circuit (BPF5, BPF8); the phase line (lda1, ldb1) of the lowpass filter circuit and the phase line (lda2, ldb2) of the highpass filter circuit of each multiplexer circuit (DIP1, DIP2) are formed on different dielectric layers of the laminate and overlap in lamination direction, and a ground electrode is formed on a layer between the different dielectric layers; and the phase line (lda1, ldb1) of the lowpass filter circuit of each multiplexer circuit (DIP1, DIP2) is made wider than the phase line (lda2, ldb2) of the respective highpass filter circuit.