An apparatus for generating a three-phase pulse-width-modulation signal for a three-phase voltage inverter employing a semiconductor switching element, the apparatus comprising: a generating unit that is adapted to generate the three-phase pulse-width-modulation signal based on a voltage command vector which is decomposed into a combination of three basic voltage vectors and a first zero vector, characterized in that the basic voltage vectors have a phase difference of 60 degrees, and the generating unit includes a creating unit that is adapted to decompose the voltage command vector into a combination of two basic voltage vectors among the three basic voltage vectors, such that the voltage command vector is present between the two basic voltage vectors, thereby allocating first production time ratios for the voltage command vector to the two basic voltage vectors to obtain two allocated basic voltage vectors and allocating a first production time ratio to the first zero vector; and a distributing unit that is adapted to create a set of three virtual voltage vectors which are summed up to be a second zero vector, the three virtual voltage vectors having equal lengths and an equal phase difference of 120 degrees, and to superimpose the two allocated basic voltage vectors onto the three virtual voltage vectors so as to make superimposed virtual voltage vectors, thereby allocating second production time ratios to the superimposed virtual voltage vectors, and to allocate a second production time ratio to the first zero vector, and the generating unit is adapted to generate the three-phase pulse-width-modulation signal based on the second production time ratios of the superimposed virtual voltage vectors and the second production time ratio of the first zero vector. a generating unit that is adapted to generate the three-phase pulse-width-modulation signal based on a voltage command vector which is decomposed into a combination of three basic voltage vectors and a first zero vector, a voltage command vector which is decomposed into a combination of three basic voltage vectors and a first zero vector, characterized in that the basic voltage vectors have a phase difference of 60 degrees, and the basic voltage vectors have a phase difference of 60 degrees, and the generating unit includes a creating unit that is adapted to decompose the voltage command vector into a combination of two basic voltage vectors among the three basic voltage vectors, such that the voltage command vector is present between the two basic voltage vectors, thereby allocating first production time ratios for the voltage command vector to the two basic voltage vectors to obtain two allocated basic voltage vectors and allocating a first production time ratio to the first zero vector; and a distributing unit that is adapted to create a set of three virtual voltage vectors which are summed up to be a second zero vector, the three virtual voltage vectors having equal lengths and an equal phase difference of 120 degrees, and to superimpose the two allocated basic voltage vectors onto the three virtual voltage vectors so as to make superimposed virtual voltage vectors, thereby allocating second production time ratios to the superimposed virtual voltage vectors, and to allocate a second production time ratio to the first zero vector, and the generating unit is adapted to generate the three-phase pulse-width-modulation signal based on the second production time ratios of the superimposed virtual voltage vectors and the second production time ratio of the first zero vector. a creating unit that is adapted to decompose the voltage command vector into a combination of two basic voltage vectors among the three basic voltage vectors, such that the voltage command vector is present between the two basic voltage vectors, thereby allocating first production time ratios for the voltage command vector to the two basic voltage vectors to obtain two allocated basic voltage vectors and allocating a first production time ratio to the first zero vector; and a distributing unit that is adapted to create a set of three virtual voltage vectors which are summed up to be a second zero vector, the three virtual voltage vectors having equal lengths and an equal phase difference of 120 degrees, and to superimpose the two allocated basic voltage vectors onto the three virtual voltage vectors so as to make superimposed virtual voltage vectors, thereby allocating second production time ratios to the superimposed virtual voltage vectors, and to allocate a second production time ratio to the first zero vector, and the generating unit is adapted to generate the three-phase pulse-width-modulation signal based on the second production time ratios of the superimposed virtual voltage vectors and the second production time ratio of the first zero vector. to create a set of three virtual voltage vectors which are summed up to be a second zero vector, the three virtual voltage vectors having equal lengths and an equal phase difference of 120 degrees, and to superimpose the two allocated basic voltage vectors onto the three virtual voltage vectors so as to make superimposed virtual voltage vectors, thereby allocating second production time ratios to the superimposed virtual voltage vectors, and to allocate a second production time ratio to the first zero vector, and the generating unit is adapted to generate the three-phase pulse-width-modulation signal based on the second production time ratios of the superimposed virtual voltage vectors and the second production time ratio of the first zero vector.