Method and device for cleaning synthesis gas obtained during gasification of biomass are disclosed. The synthesis gas is passed through a saturation device and an absorption device, both of which are fed with oil. In this way, the synthesis gas is scrubbed with oil and tar is substantially removed therefrom. The tar-containing oil which is released in this process is subjected to a cleaning step, as a result of which oil with a high percentage of tar and oil with a relatively low percentage of tar are formed. The first oil can be retuned to the gasification, and the remaining oil can be reused.