An injection-locked frequency divider is provided. The injection-locked frequency divider includes a voltage control oscillator (VCO) and a mixer. The VCO includes a LC resonance tank and a negative-resistance generator for generating a differential oscillation signal including a first and a second oscillation signals. The LC resonance tank adjusts a VCO reactance and resonates for generating the differential oscillation signal. The negative-resistance generator coupled to the LC resonance tank eliminates an equivalent resistance generated by the LC resonance tank and maintains the VCO to continuously oscillate. The mixer has a first and a second local input terminals respectively receiving the first and second injected signals included in a differential injected signal, and the first and second radio frequency input terminals respectively receiving the first and second oscillation signals for mixing the differential injected signal with the differential oscillation signal to adjust the output frequency of the differential oscillation signal.