Provided is a rent management device capable of increasing a real-estate investor' s motivation toward real-estate investment. This rent management device is for calculating and displaying a rental income from a real-estate property for each specific unit of time, and is characterized by being provided with : an input reception unit which acquires, from a user, information about a rental income of a real-estate property per specific period, a calculation start time of the rental income, a specific unit of time, and the current date and time; a first storage unit which stores said information; a calculation unit which reads said information from the first storage unit, calculates the rental income for the specific unit of time, calculates an elapsed time, calculates a cumulative rental income, and calculates the cumulative rental income every time the specific unit of time has elapsed, so as to update the cumulative rental income; a second storage unit which stores the rental income for the specific unit of time, the elapsed time, and the cumulative rental income; and an output unit which outputs the updated cumulative rental income.