To provide a Q-value measurement system for equalizing room temperature in a building, measuring Q-value of the building after construction and performing a comparative evaluation of Q-value between buildings.

The Q-value measurement system comprises: an agitator for agitating thermal energy discharged from a heater; a thermal controller for controlling thermal energy; an electric power data storage unit for measuring and storing therein electric power of the heater and agitator; a measurement unit for each room; a room thermometer for each room; an outdoor thermometer and a SAT meter for measuring outdoor temperature outside a building; a temperature data collection unit for retrieving temperature data from each thermometer; a measurement unit controller for outputting to the thermal controller in the measurement unit a control value for a heater to equalize the temperature in the building, and retrieving electric power data from the electric power data storage unit; and a Q-value measurement processor for obtaining a thermal loss coefficient for the building from the outdoor temperature and SAT temperature retrieved from the temperature data collection unit, the electric power data of the heater and agitator retrieved from the measurement unit controller, and a total floor space of the building and space capacity data of each room.