Disclosed is an adaptive modulation scheme and apparatus thereof using an Analog/Digital (AJO) converter with variable bit resolution or clock frequency, the A/D converter including a transmitter including a modulator to modulate data to be transmitted according to a modulation scheme received from a receiver, an A/D converter to convert the modulated data into an analog signal using a bit resolution or a clock frequency received from the receiver, and a radio frequency (RF) processor to transmit the analog signal to the receiver through a wireless channel and a receiver including an RF processor to receive data through a wireless channel, a calculator to calculate a Signal to Noise Ratio (SNR) of the data received through the RF processor, and a modulation controller to search a predetermined setting table for a corresponding modulation scheme and bit resolution using the calculated SNR and to transmit to a transmitter.