Provided are a plasma irradiation apparatus and plasma irradiation method capable of converting a silica precursor to a high quality silica film in a short time without thermal effects on the object being processed. This plasma irradiation apparatus 1 is provided with a plasma-generating unit 12 and an irradiation unit 80 for irradiating the plasma generated by the plasma-generating unit 12 on an object to be processed, and is characterized in that irradiation unit 80 comprises a coating part 85 capable of coating a liquid on the object being processed.