A mobile station such as a cellular phone, a communication system, and a telephone communication mode switching method that enable smooth switching between telephone communication using a public telephone line and telephone communication using the Internet shortly are provided. A mobile station control part is provided that determines whether a radio communication level of telephone communication using a public telephone line is below a first reference value, acquires, if determined so, location information of the mobile station, transmits the location information to a network server, receives wireless LAN spot information transmitted from the network server according to the location information, establishes wireless LAN connection based on the wireless LAN spot information, and establishes, if the radio communication level is determined to be below a second reference value smaller than the first reference value, a call of telephone communication using the Internet with a switching unit by wireless LAN connection.