To provide a surface treatment method capable of restoring the desired collection capacity of an electret filter by re-charging the whole of the electret filter at the time of regeneration of the electret filter.

A vacuum plasma surface treatment apparatus is equipped with a discharge electrode 2 for generating RF plasma discharge and a conductive sample stand 4 on which the electret filter 3 allowed to be spaced apart from the discharge electrode 2 by a predetermined distance is placed and the sample stand 4 is grounded. This surface treatment apparatus is used to charge the electret filter 3 for a predetermined time by vacuum plasma surface treatment to regenerate the same. Since the obtained electret filter is charged as a whole and has highly oriented electric polarization, excellent filter capacity the same as that at the time of initial production can be restored.