To provide an automatic controller capable of handling a control signal at a level that is not higher than the minimum resolution of an actuator.

This automatic controller is provided with a quantizing means for sequentially quantizing a control signal, a first judging means for judging whether the level of the quantized signal is lower than the input minimum resolution of a control object actuator, an accumulating means for sequentially accumulating the quantized signal when a judgement result is lower than the input minimum resolution, a second judging means for judging whether an accumulation result is lower than the input minimum resolution, and an accumulation result replacing means for replacing the accumulation result with a signal of minimum resolution to control the actuator and replacing an accumulation value of the accumulating means with a value obtained by subtracting a minimum resolution level from the accumulation result when the judgement result becomes equal to or more than the input minimum resolution.