Disclosed are a modem sharing device of a PDA phone capable of efficiently sharing a modem by constructing one parsing module respectively attached to a plurality of applications of the PDA phone in order to parse commands of the plurality of applications, and a method thereof. The modem sharing device of a PDA phone comprises: a plurality of applications; one parsing module for parsing commands generated by the plurality of applications and distributing; a transmission module for transmitting the distributed commands through one port; and a modem for receiving the transmitted commands.