To provide the removing device and the removing method for refrigerating machine oil in a refrigerant pipeline, in which no load due to a pressure is applied on the refrigerant pipeline and which are capable of removing the refrigerant machine oil from the refrigerant pipeline by the small amount of an oil removing agent.

A connecting tube 5 is attached to the side of one end of a gas tube 30 and a liquid tube 31 which are constituting the refrigerant pipeline 3 while a foam generating device 4 is attached to the other end side of the gas tube 30. The other end side of the liquid tube 31 is opened. Foam, into which the refrigerating machine oil removing agent is mixed, is sent from the foam generating device 4 into the gas tube 30 to separate the refrigerating machine oil from the refrigerant pipeline 3. The refrigerating machine oil is discharged out of the liquid tube 31 together with the foam and is removed from the refrigerant pipeline 3.