A counting device, including multiple counting circuit stages and a first logic operation circuit, is provided. The counting circuit stages are serially coupled in sequence. A first counting circuit stage performs a counting action according to a first clock signal and generates a first counting result. Second to Nth counting circuit stages perform counting actions according to a second clock signal, where N is a positive integer greater than 2. The first logic operation circuit provides the first counting result to be the second clock signal according to an indication signal.