A modulation method and a modulation apparatus in a phase-locked loop (PLL) provided. The modulation apparatus comprises a modulator, a crystal oscillator, a controllable R-divisor frequency divider, a controllable N-divisor frequency divider and a voltage-controlled oscillator (VCO). The crystal oscillator generates a fixed frequency oscillating signal. The controllable R-divisor frequency divider receives the oscillating signal from the crystal oscillator and divides the frequency by R. The VCO generates a frequency signal based on a voltage-controlled signal provided by the PLL and feedbacks the frequency signal to the controllable N-divisor frequency divider. The controller N-divisor frequency divider receives a feedback frequency from the VCO and divides the frequency by N. A PLL unit used to compare a frequency provided by the crystal oscillator and passed through the controllable R-divisor frequency divider, with a frequency provided by the VCO and passed through the controllable N-divisor frequency divider, for performing a phase-locked operation.