PURPOSE: To obtain a highly refined fish oil emitting little fishy smell even after the storage over a long period and utilizable as an oil-containing food such as mayonnaise and margarine by treating a fish oil with a porous polymer resin to remove the odorous component by adsorption.

CONSTITUTION: A fish oil such as tuna oil refined by conventional refining process comprising deacidification, decoloration and deodorization steps is dissolved in n-hexane and passed through a column packed with a porous polymer resin to effect the adsorption of the polar substances in the solution to the resin. The fish oil remaining in the n-hexane solution as a non-adsorbed substance is passed through the column and the resin is washed by passing n-hexane through the column. The effluent liquid and the washing liquid are joined together, concentrated under reduced pressure and subjected to steam distillation under reduced pressure to remove the precursor substances for odorous component without deteriorating the chemical structure of the oil. The objective highly refined fish oil produced by this process emits little fishy smell even after the storage over a long period and is widely utilizable as foods containing oil and fat.