A power control device includes a power supply, an integrated scanner assembly (ISA), an image forming engine including a general engine unit and a special engine unit, a main power switch, a special engine unit power switch, and a processor including an independent power controller, and the processor to control power supplied to the ISA and the general engine unit by closing the main power switch through the independent power controller, to receive specification information from the ISA activated by the supplied power, to receive state information on the image forming engine from the general engine unit activated by the supplied power, and to supply power to the special engine unit by closing the special engine unit power switch after receiving the specification information and the state information.