PURPOSE: To provide an inexpensive indoor service system for portable telephones capable of easily performing the indoor service for the portable telephones, mainly PHP terminals, even inside the buildings and underground structures where radio waves transmitted from the antenna of an outside public base station hardly reach.

CONSTITUTION: In this indoor service system for the portable telephones for performing the service to the PHP terminals by radio through the antenna 4 provided outside the main body 1 of the public base station of PHP connected to a telephone circuit 2, an outdoor relay antenna 6 is provided near the antenna 4 and an indoor relay antenna 8 is provided inside the building 5 and the underground structure where the radio waves hardly reach. The outdoor relay antenna 6 and the indoor relay antenna 8 are connected by a coaxial cable 7 and the service is performed for the PHP terminals inside the building 5 and the underground structure by the main body 1 of the public station.