A clock generation device includes a flip-flop, a clock division unit, and a clock comparator. The flip-flop generates a chip selection signal synchronized with an internal clock signal. The clock division unit generates second divided clock signals based on a first divided clock signal. The clock comparator selects ones of the second divided clock signals based on the chip selection signal. The clock division unit divides the internal clock signal based on the first divided clock signal and the selected one of the second divided clock signals.