This heat pump and dehumidifying apparatus have small energy-consumed per moisture-removed ratios. Their components include a pressurizer for raising refrigerant pressure; a condenser for condensing refrigerant, thereby heating a high-temperature heat source fluid; an evaporator for evaporating refrigerant to cool a low-temperature heat source fluid; and a heat exchanger in a refrigerant path connecting the condenser and the evaporator for evaporating and condensing refrigerant under an intermediate pressure between the condensor pressure and the evaporator pressure. The low-temperature heat source fluid is successively cooled by the heat exchanger, cooled by the evaporator, and heated by the heat exchanger. This fluid can be precooled by the heat exchanger before cooling in the evaporator, and heat removed during precooling can be returned to the fluid after cooling by the evaporator.