Provided are a mobile terminal testing apparatus, a mobile terminal testing system, and a control method for a mobile terminal testing apparatus which can prevent the level of the multiplexed signal transmitted and received to and from a mobile terminal from being misidentified. Provided is a mobile terminal testing apparatus which tests a waveform of a multiplexed signal obtained by multiplexing a uplink signal transmitted by a mobile terminal and a downlink signal transmitted to the mobile terminal by time division multiplexing, in which area information 21 of a first display mode indicating the uplink signal and area information 22 of a second display mode indicating the downlink signal are displayed in association with the waveform 23 of the multiplexed signal, on the display unit.