Disclosed is a parallel analog-to-digital converter in which a plurality of comparators are divided into a plurality of groups each consisting of a predetermined number of comparators, and outputs of at least these comparators belonging to the same group are added in an analog or digital fashion. Whether or not the result of addition of the outputs of the comparators exceeds a predetermined threshold level is decided in an analog or digital fashion so as to determine high-order and low-order bits of a digital output signal of the converter on the basis of the result of decision.