To provide a portable device for outputting a charging rate which facilitates the use of commercial power sources of normal households, factories, companies, etc. when charging a battery of an electric vehicle and can promote spread of electric vehicles.

This portable device 10 for outputting a charging rate includes a voltage detecting means 19, which detects a voltage class of the power supplied from a power supply source 30; a unit price determining means 21 which determines an approximate unit price of a power rate, on the basis of the result of detection of the voltage detecting means 19; a power quantity measuring means 20, which measures the quantity of the power supplied from the power supply source 30; a power rate calculating means 21, which calculates the power rate by multiplying the approximate unit price of the power rate determined by the unit price determining means 21 by the quantity of the power measured by the power quantity measuring means 20; and a power rate output means 23, which outputs the power rate calculated by the power rate calculating means 21.