An apparatus and method are provided for monitoring an antenna state of a mobile station. A resister (110) may be provided between a battery voltage terminal and a power source voltage terminal of a power amplifier (20). A voltage level corresponding to a dropped amount of a voltage due to the resister may be generated and compared with a previously stored voltage level to determine whether current consumption of the power amplifier has been increased. If the increased amount of the current consumption of the power amplifier is large, the currently connected antenna may be determined to be in an abnormal state and a transmission path may be switched to another antenna. If two antennas provided in the mobile communication are in an electrically abnormal state, a baseband chip (200) may inform a user of the abnormal state of the antenna. Accordingly, an output level degradation generated when the antenna is operated in an electrically abnormal state and shortening of the life span of a battery can be prevented. Thus, performance of an output terminal can be enhanced.