In an interleaving power factor corrector, a control device interleavingly drives first and second converting circuits such that the power factor corrector generates a voltage output (Vo), and includes first and second control modules generating respectively first and second driving signals (Q_master, Q_slave) that correspond respectively to first and second control signals for controlling operations of power switches of the first and second converting circuits. A phase modulating module generates a reset signal (S_PTCL) based on an inverted first driving signal (Qn_master) and a feedback compensation signal (Vcomp) outputted by the first control module, and a reset signal (S_syn) outputted by the second control module. When one of the reset signals (S_syn, S_PTCL) has a predetermined level, the second driving signal (Q_slave) has a level for switching the power switch of the second converting circuit to an OFF-mode.