The present technology relates to an A/D converter, a solid-state image pickup device and a method of driving the same, and an electronic apparatus which are capable of reducing power consumption while reducing a circuit size. A comparator compares a reference voltage with an input voltage, the reference voltage having a ramp waveform whose voltage value varies with time, a lower-bit storage element holds a count value in a predetermined count pattern, based on an output signal from the comparator, a Gray code binary conversion circuit converts the count value in the count pattern held by the lower-bit storage element into binary data, and a storing operation control circuit supplies a pulse signal corresponding to the binary data obtained by conversion in the Gray code binary conversion circuit to a lower-bit U/D CNT. The present technology is applicable to, for example, an image sensor storing a count value in a storage element with use of a Gray code or a phase shift code as a clock signal.