Provided is a private branch exchange capable of independently adjusting call voice level and call quality according to a connection type of a communication line or a telephone. The private branch exchange includes an audio quality characteristic configuration DB (116) for storing audio quality adjustment values of gain circuits (112 and 122) and an echo canceller circuit (121) for which optimal call quality can be obtained according to a combination for each group of telephone type and line type to connect for a telephone call, and a connection path DB (117) for storing information related to a connection path determined by a combination of a telephone and a communication line to connect for the telephone call, in which if there is a connection request from the telephone or the communication line, the connection path DB (117) is referred to obtain, by referring to the audio quality characteristic configuration DB (116), audio quality adjustment values to be set for the gain circuits (112 and 122) and the echo canceller circuit (121) which exist on the connection path that is determined, to perform settings for the gain circuits (112 and 122) and the echo canceller circuit (121).