To securely and sufficiently damp pressure fluctuation caused by pulsation of refrigerant under the conditions of large flow and a large differential pressure and under the conditions that refrigerant temperature is greatly fluctuated.

A refrigerant pump system 1 has an electric motor 4 and a pump mechanism 5 incorporated into a sealed vessel 3 to suck refrigerant through a suction pipe 14 and discharge it from a discharge pipe 15. A plurality of pulsation reducing vessels 18a, 18b provided with sheath heaters 19 as heating means, respectively, are connected with the discharge pipe 15 among the suction pipe 14 and the discharge pipe 15.