Nonhydrocarbon gas separation device and nonhydrocarbon gas separation method

Provided is a non-hydrocarbon gas separation device or the like capable of separating a non-hydrocarbon gas from a natural gas containing a heavy hydrocarbon. The non-hydrocarbon gas separation device is configured to separate a non-hydrocarbon gas from a natural gas. The natural gas containing a heavy hydrocarbon, the heavy hydrocarbon having 5 or more carbon atoms, is supplied to a separation module (2). The natural gas having been separated from the non-hydrocarbon gas is allowed to outflow from the separation module (2), and the non-hydrocarbon gas having been separated from the natural gas is discharged from the separation module (2). An inorganic membrane (20), which is housed in the separation module (2), and is made of an inorganic material is configured to allow the non-hydrocarbon gas contained in the natural gas to permeate therethrough to a discharge side, and to allow the natural gas having been separated from the non-hydrocarbon gas to flow to an outflow side. A heating unit (3) is configured to heat the natural gas to be supplied to the separation module (2) so that a temperature in the separation module (2) is kept at a temperature higher than a dew point temperature of the heavy hydrocarbon.