PCT No. PCT/JP96/00320 Sec. 371 Date Aug. 7, 1997 Sec. 102(e) Date Aug. 7, 1997 PCT Filed Feb. 13, 1996 PCT Pub. No. WO96/25474 PCT Pub. Date Aug. 22, 1996A biodegradable lubricating base oil obtained by carrying out an addition reaction of an alkylene oxide and a transesterification in a mixture of fats and oils, a polyhydric alcohol or an aliphatic carboxylic acid, and an alkylene oxide, the mixture containing 5 to 150 mol of the alkylene oxide to 1 mol of the fats and oils; a biodegradable lubricating base oil obtained by carrying out esterification of all or part of the hydroxyl group in the above fats and oils derivative using an aliphatic carboxylic acid or ester derivative thereof. Further, a biodegradable lubricating oil composition containing the biodegradable lubricating base oil and the use thereof are also described.