An antenna switch module connected to a common antenna for switching the connection of the antenna to a transmission circuit or a receiving circuit in plural transmitting/receiving systems having different passbands, comprising a diplexer circuit comprising a low-pass filter and a high-pass filter; a first switch circuit connected to the low-pass filter and for switching a transmitting line and a receiving line, a second switch circuit connected to the high-pass filter for switching a transmitting line and a receiving line; a third switch circuit connected to the first switch circuit for switching the receiving line from the first switch circuit; and a fourth switch circuit connected to the second switch circuit for switching the receiving line from the second switch circuit; at least part of transmission lines constituting LC circuits in the diplexer circuit and the first and second switch circuits being electrode patterns formed in a multilayer substrate constituted by plural dielectric layers; and chip elements constituting part of the LC circuits, diode elements constituting the first and second switch circuits, and semiconductor elements constituting the third and fourth switch circuits being mounted onto the multilayer substrate.