A vehicle opening/closing body control device includes: an assist control unit that applies a voltage to a motor which drives an opening/closing body of a vehicle so as to perform an assist opening/closing actuation that assists a manual operation force with respect to the opening/closing body for performing an opening/closing actuation of the opening/closing body; and an actuation finish determination unit that determines whether or not a finish condition of the assist opening/closing actuation is satisfied, based on a change amount of an opening/closing speed of the opening/closing body per unit time, in which the assist control unit stops applying the voltage to the motor in a case where the finish condition of the assist opening/closing actuation is satisfied.