A center-of-gravity detection system comprising: a container cargo vehicle (11, 12) comprising a container capable of carrying the cargo and a container chassis on which said container is placed and which is adapted to be towed by a towing vehicle; and an arithmetic unit; a shake detector configured to detect the angular velocity of shakes in the directions of the self-weight and width of said towed container cargo vehicle (11, 12) during travel of said towed container cargo vehicle (11, 12); and wherein when the shake in the self-weight direction corresponds to a vertical reciprocation motion in which the center of gravity of said container cargo vehicle (11, 12) is a mass point and the shake in the width direction corresponds to a horizontal simple pendulum motion in which the axle center of said container cargo vehicle (11, 12) is a support point and the center of gravity of said container cargo vehicle (11, 12) is a mass point, characterised in that said arithmetic unit is configured to derive, based upon a first expression which represents a relationship between the frequency of the simple pendulum motion and the location of the center of gravity of said container cargo vehicle (11, 12) with respect to the travel direction of said container, the location of the center of gravity of said container cargo vehicle (11, 12) with respect to the travel direction of said container, and to derive, based upon a second expression which represents a relationship between the frequency of the reciprocation motion, the frequency of the simple pendulum motion, the central angle of the simple pendulum motion and the location of the center of gravity of said container cargo vehicle (11, 12) with respect to a cross-section surface perpendicular to the travel direction of said container, the location of the center of gravity of said container cargo vehicle (11, 12) with respect to a cross-section surface perpendicular to the travel direction of said container. a container cargo vehicle (11, 12) comprising a container capable of carrying the cargo and a container chassis on which said container is placed and which is adapted to be towed by a towing vehicle; and an arithmetic unit; a shake detector configured to detect the angular velocity of shakes in the directions of the self-weight and width of said towed container cargo vehicle (11, 12) during travel of said towed container cargo vehicle (11, 12); and wherein when the shake in the self-weight direction corresponds to a vertical reciprocation motion in which the center of gravity of said container cargo vehicle (11, 12) is a mass point and the shake in the width direction corresponds to a horizontal simple pendulum motion in which the axle center of said container cargo vehicle (11, 12) is a support point and the center of gravity of said container cargo vehicle (11, 12) is a mass point, characterised in that said arithmetic unit is configured to derive, based upon a first expression which represents a relationship between the frequency of the simple pendulum motion and the location of the center of gravity of said container cargo vehicle (11, 12) with respect to the travel direction of said container, the location of the center of gravity of said container cargo vehicle (11, 12) with respect to the travel direction of said container, and to derive, based upon a second expression which represents a relationship between the frequency of the reciprocation motion, the frequency of the simple pendulum motion, the central angle of the simple pendulum motion and the location of the center of gravity of said container cargo vehicle (11, 12) with respect to a cross-section surface perpendicular to the travel direction of said container, the location of the center of gravity of said container cargo vehicle (11, 12) with respect to a cross-section surface perpendicular to the travel direction of said container.