According to a dot interpolation control system for dot-interpolating a character pattern in a predetermined dot matrix form along at least the main scanning direction or the subscanning direction, there is provided a pair of registers for designating initial addresses of interpolated dots along the main scanning direction, another pair of registers for designating a dot pitch along the main scanning direction, and still another pair of registers for designating a dot pitch along the subscanning direction. Data pairs of x and y components, which selectively include trigonometric function data representing a designated rotation or inclination angle, are set in the corresponding registers. Dot interpolation of a character pattern is performed by main scanning and subscanning in accordance with the contents of the respective registers, thereby obtaining a rotated or inclined character on the basis of the designated angle.