To provide a unit for prepaid system to which a multi-function such as the identification function of a transmitting person and a telephone directory are added bisides dissolving complicatedness of connection in a prepaid system mobile communication system.

The unit for prepaid system 30 is connected to mobile communication equipment 1; and can transmit at least an access number, an ID (identification) number, and a password through the mobile communication equipment. The prepaid unit has an operation part 31, a unit control part 32 and a storage part 34. The unit control part calls specific data from the storage part on the basis of an input signal from the operation part, and transmits data or data processed from the data from this unit to the mobile communication equipment.