A controller of a heat pump utilization system, the controller controlling the heat pump utilization system including a heat source side circulation circuit through which a first heat medium circulates and a use side circulation circuit through which a second heat medium circulates, the heat source side circulation circuit being connected with at least a frequency variable compressor and an intermediate heat exchanger in which the first heat medium and the second heat medium exchange heat, the use side circulation circuit being connected with at least a circulation pump having a variable rotation speed, the intermediate heat exchanger, and an indoor heat exchanger in which the second heat medium and indoor air exchange heat, the controller characterised by comprising: a room temperature control unit configured to generate a heat amount command, based on a room temperature and a set room temperature that is a target value of the room temperature; a frequency command generation unit configured to generate a frequency command to the compressor, based on the heat amount command; a circulation temperature command generation unit configured to generate a circulation temperature command that is a command of circulation temperature of the second heat medium, based on the heat amount command; a circulation temperature control unit configured to generate a rotation speed command to the circulation pump by feedback control using at least a proportional coefficient, based on the circulation temperature and the circulation temperature command; and a correction coefficient generation unit configured to generate a correction coefficient, based on the circulation flow rate of the second heat medium and a preset circulation flow rate reference value, wherein the circulation temperature is any of an inflow temperature of the second heat medium flowing into the intermediate heat exchanger, an outflow temperature of the second heat medium flowing out of the intermediate heat exchanger, and a temperature difference between the outflow temperature and the inflow temperature, the circulation temperature control unit is configured to calculate the proportional coefficient by multiplying a preset proportional coefficient reference value by the correction coefficient, the correction coefficient generation unit is configured to generate the correction coefficient such that when the circulation flow rate increases beyond the circulation flow rate reference value, the proportional coefficient increases beyond the proportional coefficient reference value, while when the circulation flow rate decreases beyond the circulation flow rate reference value, the proportional coefficient decreases beyond the proportional coefficient reference value. a room temperature control unit configured to generate a heat amount command, based on a room temperature and a set room temperature that is a target value of the room temperature; a frequency command generation unit configured to generate a frequency command to the compressor, based on the heat amount command; a circulation temperature command generation unit configured to generate a circulation temperature command that is a command of circulation temperature of the second heat medium, based on the heat amount command; a circulation temperature control unit configured to generate a rotation speed command to the circulation pump by feedback control using at least a proportional coefficient, based on the circulation temperature and the circulation temperature command; and a correction coefficient generation unit configured to generate a correction coefficient, based on the circulation flow rate of the second heat medium and a preset circulation flow rate reference value, wherein the circulation temperature is any of an inflow temperature of the second heat medium flowing into the intermediate heat exchanger, an outflow temperature of the second heat medium flowing out of the intermediate heat exchanger, and a temperature difference between the outflow temperature and the inflow temperature, the circulation temperature control unit is configured to calculate the proportional coefficient by multiplying a preset proportional coefficient reference value by the correction coefficient, the correction coefficient generation unit is configured to generate the correction coefficient such that when the circulation flow rate increases beyond the circulation flow rate reference value, the proportional coefficient increases beyond the proportional coefficient reference value, while when the circulation flow rate decreases beyond the circulation flow rate reference value, the proportional coefficient decreases beyond the proportional coefficient reference value.