This underwater device is twin-motor underwater floating-type power generation device that is provided with: a device main body that is equipped with a pair of pods that have a turbine, and with a connecting beam that connects these pods together in parallel with each other; a sinker; and tether cables that tether the device main body to the seabed via this sinker. The respective turbines of the pods are each provided with variable pitch turbine blades. This device is also provided with a depth meter that detects deviation in posture in the roll direction that is generated in the pair of pods, and a posture controller that controls the pitch of the variable pitch turbine blades of the respective turbines so as to nullify any deviation in posture in the roll direction that has been generated in the pair of pods and has been detected by the depth meter.
