In a communication apparatus, a specific bit is detected from a communication data decoded in a low-speed state of a communication speed. The specific bit is a bit having undergone an inverse change in a logical value. A signal waveform of the communication signal is acquired, which is recorded in a memory and corresponds to the specific bit. Then, a sampling point of the communication signal in a high-speed state of the communication signal is calculated based on (i) the acquired signal waveform and (ii) a logical value of the specific bit.