This invention provides a ground-speed measuring apparatus for a vehicle that can detect a velocity along the movement of the vehicle (in the fore direction), a velocity across the movement of the vehicle (in the athwartships direction), a side-skid angle of the vehicle, and an angular velocity of the vehicle.A ground-speed measuring apparatus comprising three or more transceivers each of which contains a transmitter for transmitting a wave and a receiver for receiving a reflection of the wave transmitted from the transmitter, wherein at least three of said transceivers are placed outside a cylindrical area whose axis of symmetry passes through a point on the floor of the vehicle, three straight lines which respectively pass through said transceivers perpendicularly thereto intersect with each other or skewed in said cylindrical area, and the transmitter of each transceiver is at a preset angle with the floor of the vehicle.