To reduce the sizes of a data converting method during a serial/ parallel conversion that especially requires high speed operations, a serial/ parallel converting IC, an image forming circuit and a display device in a data inputting circuit for the elements of the display device that uses spatial optical modulation elements.

Data are inputted into spatial optical modulation elements that are used for the modulation of the display device and the data to be supplied as serial data are converted into the number of parallel data required for the spatial optical modulation elements. The serial/parallel conversion is used for an n th stage (where n≥2) so that the serial/parallel conversion element of a last stage outputs parallel outputs equal to or greater than m/2(n-1) for a parallel data number m required by the spatial optical modulation elements. Thus, the size and the cost of the circuit which converts serial data into parallel data and supplies the data to the spatial optical modulation elements used in the display device are reduced.