A high-frequency switch module includes an ESD device, a switch IC, and a SAW filter element that are mounted on the surface of a multilayer substrate. A ground-side land for the ESD device is connected to an external-connection ground electrode for the ESD device by via holes and plane electrode patterns. A ground connection land for the switch IC and a ground connection land for the SAW filter element are connected to a common inner ground electrode by via holes, and are connected to a common external-connection ground electrode by via holes and another common inner ground electrode.