Method for cleaning oil-deposited material

A method of cleaning an oil-deposited material comprising the steps of

• applying a cleaning agent which floats and separates oil consisting essentially of 25 to 90% by weight of at least one of compounds selected from the group consisting of pyrrolidones, .gamma.-butyrolactone and N,N-dimethylacetamide, and 10-75% by weight of water, to an oil-deposited surface of the material to be cleaned;
• eliminating at least a portion of the deposited cleaning agent from said material to be cleaned by physical means;
• water-washing with , steam or water and steam;
• removing oil which has been separated and floated from the oil-deposited material from said cleaning agent to provide recycled cleaning agent, and
• repeating the above steps at least once with said recycled cleaning agent.