A positioning apparatus used with a movable object to determine a position of the movable object, the positioning apparatus comprising: a satellite positioning device that calculates a satellite positioning coordinate based on a navigation signal received by a navigation signal receiver; a movement quantity calculator that acquires a signal detected by an inertial sensor (20, 30), and sequentially calculates a movement quantity of the movable object by inertial navigation from a moment when the navigation signal is received until a moment when the signal from the inertial sensor is received; a virtual reference point determinator that sequentially determines a coordinate of a virtual reference point after receiving the navigation signal; a position determinator that determines the position of the movable object sequentially by adding the movement quantity of the movable object to the coordinate of the virtual reference point; and a positioning coordinate reliability calculator that calculates reliability of the satellite positioning coordinate, wherein the virtual reference point determinator determines the coordinate of the virtual reference point by multiplying respective weighting factors with a position of the movable object, which is determined, by the position determinator, when the navigation signal is received, and with the satellite positioning coordinate and then adding the weighted positions together, and increases the one of the respective weighting factors to be used to multiply with the satellite positioning coordinate in incremental steps, wherein the virtual reference point determinator calculates the other of the respective weighting factors to be used to multiply with the position of the movable object which is determined when the navigation signal is received, by using a first factor calculating expression, which includes a negative term having a value changed in a decreasing manner based on number of times the movement quantity calculator calculating the movement quantity after receiving the navigation signal; wherein the virtual reference point determinator calculates the one of the respective weighting factors to be used to multiply with the satellite positioning coordinate by using a second factor calculating expression, which includes a positive term having a value changed in an increasing manner based on the number of times the movement quantity calculator calculating the movement quantity after receiving the navigation signal, wherein each of the first factor calculating expression and the second factor calculating expression includes an offset term as a constant term regardless of the number of times the movement quantity calculator calculating the movement quantity, wherein the virtual reference point determinator increases a value of the offset term as the reliability of the satellite positioning coordinate increases. a satellite positioning device that calculates a satellite positioning coordinate based on a navigation signal received by a navigation signal receiver; a movement quantity calculator that acquires a signal detected by an inertial sensor (20, 30), and sequentially calculates a movement quantity of the movable object by inertial navigation from a moment when the navigation signal is received until a moment when the signal from the inertial sensor is received; a virtual reference point determinator that sequentially determines a coordinate of a virtual reference point after receiving the navigation signal; a position determinator that determines the position of the movable object sequentially by adding the movement quantity of the movable object to the coordinate of the virtual reference point; and a positioning coordinate reliability calculator that calculates reliability of the satellite positioning coordinate, wherein the virtual reference point determinator determines the coordinate of the virtual reference point by multiplying respective weighting factors with a position of the movable object, which is determined, by the position determinator, when the navigation signal is received, and with the satellite positioning coordinate and then adding the weighted positions together, and increases the one of the respective weighting factors to be used to multiply with the satellite positioning coordinate in incremental steps, wherein the virtual reference point determinator calculates the other of the respective weighting factors to be used to multiply with the position of the movable object which is determined when the navigation signal is received, by using a first factor calculating expression, which includes a negative term having a value changed in a decreasing manner based on number of times the movement quantity calculator calculating the movement quantity after receiving the navigation signal; wherein the virtual reference point determinator calculates the one of the respective weighting factors to be used to multiply with the satellite positioning coordinate by using a second factor calculating expression, which includes a positive term having a value changed in an increasing manner based on the number of times the movement quantity calculator calculating the movement quantity after receiving the navigation signal, wherein each of the first factor calculating expression and the second factor calculating expression includes an offset term as a constant term regardless of the number of times the movement quantity calculator calculating the movement quantity, wherein the virtual reference point determinator increases a value of the offset term as the reliability of the satellite positioning coordinate increases.