To provide an apparatus for evaluating the coating properties of a film, so as to be capable of deciding the coating properties of the film quantitatively or semi-quantitatively for accurate evaluation of, for example, the corrosion resistance of a magnetic recording medium.

The apparatus for evaluating the coating properties of the film is equipped with a gas mixer 4 for mixing the dry corrosive gas and humid gas, respectively sent in from a corrosive gas generation part 2 and a humid gas generation part 3 to adjust the concentration and humidity of the mixed gas and a gas exposure part 5 for exposing a sample to the prepared gas sent from the gas mixer 4. The gas mixer 4 has an expanded part interposed between a gas sending-in pipe and a gas mixing container for reducing gas flowing velocity to expand flux and the gas exposure part 5 has a porous plate for uniformizing the flow, concentration and humidity of the gas.