To provide a plasma-controlling method which comparatively easily provides a means for improving the thickness uniformity of a film formed with the use of a plasma CVD apparatus, while focusing attention on a measurement quantity related to the film thickness uniformity associated with a change of a film-forming condition, provides an adequate uniformity of characteristics by keeping up with the change of the characteristics, which means the change of an absolute value of a voltage Vpp between peaks and plasma distribution according to the time when a lot is produced, and improves the yield of a product.

When controlling the distribution of plasma 205 generated by a high-frequency power applied to a high-frequency electrode 210, in a vacuum vessel 201 that has the high-frequency electrode 210 which is connected to a high-frequency power supply source and has an earth electrode 211 which faces the high-frequency electrode 210 and is connected to an earth potential, this plasma-controlling method controls the distribution of the plasma when the plasma is generated, on the basis of the voltage Vpp between the peaks in each electrode, which has been measured with the use of a plurality of peak voltage measuring parts placed on the high-frequency electrode 210 or/and the earth electrode 211.