A refrigerant compressor is configured such that a compressor unit is installed in a hermetically sealed container, an HFC type refrigerant or a mixture thereof and a refrigerator oil having compatibility with the refrigerant are charged into the hermetically sealed container, and the refrigerator oil essentially comprises a polyvinyl ether type compound having structural units represented by the following general formula (1): , wherein n is an integral number in the range of 1 or more, R1 to R3 are each a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms and may be the same or different, R4 is an alkyl group having 1 to 4 carbon atoms, and units in which R4 is an alkyl group having 1 to 2 carbon atoms are 40 to 100 % and units in which R4 is an alkyl group having 3 to 4 carbon atoms are 0 to 60 %. As a result, the generation of a carboxylic acid caused by thermal cracking or hydrolysis due to frictional heat generated by sliding members is prevented and the generation of sludge is thereby suppressed.