A fuser-controlling apparatus for generating a power synchronization signal and detecting a power voltage. The fuser-controlling apparatus comprises a power synchronization signal generation circuit for outputting a power synchronization signal for synchronizing fuser operations with a power voltage, a power voltage detection circuit for detecting a level of the power voltage and for outputting a level of the power voltage, and a control unit for controlling a voltage to the fuser in a phase control manner based on the power synchronization signal and the detected level of the power voltage. The fuser-controlling apparatus can produce a power synchronization signal at the zero-crossing points of the power voltage regardless of the levels and frequencies of the power voltage. Accordingly, the fuser-controlling apparatus can instantaneously perform phase and power controls based on such a power synchronization signal, resulting in improvements to the power factor and flicker characteristics of the system.