The invention relates to an apparatus for argon-plasma coagulation in which working gas is supplied to a tissue that is to be treated by passage through gas-supply devices (20) in a supply-flow direction, and the working gas flows out of a distal end of the gas-supply devices. This apparatus for argon-plasma coagulation is further developed with the aim of preventing contamination of the gas-supply devices by working gas, bodily gases and/or bodily liquids. For this purpose at least one obstructor (30) is provided, which is or can be connected to the gas-supply devices and serves to obstruct a flow of gas and/or liquid into the gas-supply devices, against a supply-flow direction.