A combined heat and power system is provided with a Rankine cycle passage, a heat medium passage, an evaporator, an expander, a condenser, a pump, a temperature sensor, a sensor, and a controller. The evaporator receives the heat from the heat medium to heat a working fluid. The temperature sensor detects the temperature of the heat medium after radiating heat for heating the working fluid. The sensor detects the pressure of the working fluid flowing between the outlet of the evaporator and the inlet of the expander. The controller adjusts the rotation speed of the pump based on the temperature detected by the temperature sensor, and in addition, adjusts the rotation speed of the expander based on the pressure detected by the sensor.