This paper describes details of an Autonomous Underwater Vehicle (AUV) named AQUA EXPLORER 2 (AE-2) for inspection of underwater cables. AE2 can track cables by detecting the magnetic field induced by an AC current flowing in the cable, and can continuously measure the burial depth of the cable. The vehicle is monitored and controlled through an acoustic link between the vehicle and a mother vessel. The operating depth is 500 meters, and it can continuously dive up to 24 hours. According to the precision analysis of the cable location system using the magnetometers, it became clear that installation error of magnetometers gave big influence to the precision of the cable positioning. Using fluid characteristic measured by scale model test, motion simulations were performed using the linearized motion equation of the AUV. The results of field test and these simulations had good agreement. As a result of real submarine cable investigation, it became clear that AUV could trace the cable precisely using Fuzzy controller even if the tide from the side was big.