A method of measuring a call delay time by synchronizing times of a replaying part and a recording part in a call delay time measuring device using an interrupting hardware method. The method includes reading an original WAV file when a replaying CPU receives a command, waiting for writing to a DAC buffer of a replaying CODEC, transferring a signal of recording-ready to a recording CPU, generating a recording WAV file by the recording CPU, waiting for reading from an ADC buffer of a recording CODEC, transferring a signal of complete recording-ready to the replaying CPU, recording the original WAV file, replaying the original WAV file and simultaneously transferring a signal of recording-start to the recording CPU, and reading audio data from the ADC buffer of the recording part by the recording CPU and recording the audio data to the recording WAV file.