This paper deals with a deposition method of lubricant during finishing electrical discharge machining (EDM) to produce parts for ultrahigh vacuum such as space environment. EDM with powder suspended in working oil has been widely used to smooth a surface and to deposit a hard layer. In this study, a solid lubricant, molybdenum disulfide (MoS2) powder is mixed in working oil instead of silicone, titanium or tungsten to deposit lubricant layer on carbon steel and stainless steel. Influence of electrical conditions in EDM and powder concentration on the deposition is investigated experimentally. MoS2 is observed on both steels. Electrical conditions to deposit MoS2 are similar to those with silicon powder, that is, a high open circuit voltage, a small discharge current, a short pulse duration and a medium pulse interval. Smoother surface can be obtained by adding aluminum powder to the mixture of MoS2 powder and working oil. In a friction test, a surface finished with a mixture of MoS2 and working oil has a smaller friction coefficient than that with normal working oil.