An underwater traveling vehicle comprising: a vehicle body endless track means which is rotatably mounted to the vehicle body; drive means which is provided in the vehicle body so as to drive the endless track means; a thruster which is provided in the vehicle body; and measurement means (5, 6) for measuring the state of the vehicle body; characterized by comprising: storage means configured to store the initial state of the vehicle body on land; and control means for controlling the thrust force or drive direction of the thruster based on outputs received from the storage means and the measurement means (5, 6), wherein the control means has determination means configured to determine whether the attitude of the vehicle body is stable or not based on outputs received from the storage means and the measurement means (5, 6), the storage means stores thresholds defining, respectively for each weight of the underwater traveling vehicle, the boundary between stable and unstable regions based on the relationship between the gravity center position and buoyancy center position, and the determination means is configured to compare 2. the gravity center and buoyancy center positions of the underwater traveling vehicle in water with the thresholds, respectively, to determine whether the attitude of the vehicle body is stable or not. a vehicle body endless track means which is rotatably mounted to the vehicle body; drive means which is provided in the vehicle body so as to drive the endless track means; a thruster which is provided in the vehicle body; and measurement means (5, 6) for measuring the state of the vehicle body; characterized by comprising: storage means configured to store the initial state of the vehicle body on land; and control means for controlling the thrust force or drive direction of the thruster based on outputs received from the storage means and the measurement means (5, 6), wherein the control means has determination means configured to determine whether the attitude of the vehicle body is stable or not based on outputs received from the storage means and the measurement means (5, 6), the storage means stores thresholds defining, respectively for each weight of the underwater traveling vehicle, the boundary between stable and unstable regions based on the relationship between the gravity center position and buoyancy center position, and the determination means is configured to compare 2. the gravity center and buoyancy center positions of the underwater traveling vehicle in water with the thresholds, respectively, to determine whether the attitude of the vehicle body is stable or not. storage means configured to store the initial state of the vehicle body on land; and control means for controlling the thrust force or drive direction of the thruster based on outputs received from the storage means and the measurement means (5, 6), wherein the control means has determination means configured to determine whether the attitude of the vehicle body is stable or not based on outputs received from the storage means and the measurement means (5, 6), the storage means stores thresholds defining, respectively for each weight of the underwater traveling vehicle, the boundary between stable and unstable regions based on the relationship between the gravity center position and buoyancy center position, and the determination means is configured to compare 2. the gravity center and buoyancy center positions of the underwater traveling vehicle in water with the thresholds, respectively, to determine whether the attitude of the vehicle body is stable or not.