A heat source device is provided with a differential pressure sensor (41) that measures the differential pressure between an inlet pressure and an outlet pressure for the chilled water in an evaporator (26) and with a control device (30). The control device (30) possesses the coefficient of loss for the evaporator (26) and is provided with a chilled-water flow-rate computing portion (52) that calculates a chilled-water flow rate at the evaporator (26) on the basis of the coefficient of loss and the differential pressure output from the differential pressure sensor (41); a control-command computing portion (55) that generates a control command by using a specification heating-medium flow rate that is set in advance; and a control-command correcting portion (56) that corrects the control command generated by the control-command computing portion (55) on the basis of the difference between the chilled-water flow rate calculated by the chilled-water flow-rate computing portion (52) and a specification chilled-water flow rate that is set in advance.
