An object is to provide in a positioning device of a moving body such as a vehicle, a technique which can modify a built-in clock error of a moving body to increase accuracy of a velocity. The positioning device includes a built-in clock error estimating unit which estimates a built-in clock error of the vehicle as a built-in clock error based on a difference between a delta range and a calculated range rate, and a range rate estimating unit which estimates a vehicle stop range rate based on position and velocity of GPS satellite based on transmission signal and a vehicle position, and modifies a calculated range rate, based on the built-in clock error. Further, the positioning device includes an own vehicle velocity calculating unit which calculates own vehicle velocities in three axial directions which form an orthogonal coordinate system, based on a navigation matrix, the vehicle stop range rate and the modified calculated range rate.