A wireless terminal device having a simple configuration with at least two antennas, a single receiver, and a single reception level measuring section, which is capable of performing transmission and reception antenna diversity without a break of communication. The wireless terminal device, which communicates with a base station, comprises a reception system and a transmission system. The reception system includes a receiver, despreading section, a PN generator, and a BCH reception level measuring section. The BCH reception level measuring section measures a reception level of the broadcast channel. The transmission system includes a transmitter, a spreading section, and a PN generator. Either of two antennas is selected by a controller and an antenna switch. When a measured value of the broadcast channel via the selected antenna is equal to or less than a threshold value, the controller switches the working antenna to the other antenna, and obtains a measured value of a reception level of the other antenna during a transmission gap. Subsequently, when the first measured value is more than the second measured value, the controller switches to the antenna having a measured value higher than the other antenna to some extent.