An object of the invention is to limit a current flowing in a booster converter circuit for a vehicle within a predetermined range. In the booster converter circuit for a vehicle including a battery that outputs a DC voltage; a switching unit having a switching element to be controlled to ON or OFF; an inductive element unit being connected between the battery and the switching unit and including an inductive element; a switching control unit that controls the switching element, an output voltage measuring unit that measures an output voltage of the booster converter circuit for a vehicle is provided, and the duty ratio determining device obtains a control duty ratio with respect to the switching element on the basis of a measured output voltage value so that a value of a converter current flowing through a path from the battery to the switching unit falls within a predetermined range.